High Performance
10-Bit Display Interface
AD9984A
Rev. 0
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2007 Analog Devices, Inc. All rights reserved.
FEATURES
10-bit, analog-to-digital converters
170 MSPS maximum conversion rate
Low PLL clock jitter at 170 MSPS
Automatic gain matching
Automated offset adjustment
2:1 input mux
Power-down via dedicated pin or serial register
4:4:4, 4:2:2, and DDR output format modes
Variable output drive strength
Odd/even field detection
External clock input
Regenerated Hsync output
Programmable output high impedance control
Hsyncs per Vsync counter
Sync-on-green (SOG) pulse filter
Pb-free package
APPLICATIONS
Advanced TVs
Plasma display panels
LCDTV
HDTV
RGB graphics processing
LCD monitors and projectors
Scan converters
FUNCTIONAL BLOCK DIAGRAM
SYNC
PROCESSING
PLL
POWER
MANAGEMENT
SOGOUT
ODD/EVEN FIELD
HSOUT
VSOUT/A0
VOLTAGE
REFS
SERIAL REGISTER
SDA
SCL
FILT
CLAMP
EXTCK/COAST
HSYNC0
HSYNC1
AD9984A
Y/GREEN
OUT
Cb/Cr/RED
OUT
REFHI
REFLO
DATACK
2:1
MUX
Pr/RED
IN0
Pr/RED
IN1
Y/GREEN
IN0
Y/GREEN
IN1
VSYNC1
VSYNC0 2:1
MUX
SOGIN0
SOGIN1 2:1
MUX
OUTPUT DATA FORMATTER
Cb/BLUE
OUT
CLAMP 10
10 AUTO OFFSET
AUTO GAIN
10-BIT
ADC
PGA
Pb/BLUE
IN0
Pb/BLUE
IN1
2:1
MUX
CLAMP 10
10 AUTO OFFSET
AUTO GAIN
10-BIT
ADC
PGA
2:1
MUX
CLAMP 10
10 AUTO OFFSET
AUTO GAIN
10-BIT
ADC
PGA
2:1
MUX
06476-001
Figure 1.
GENERAL DESCRIPTION
The AD9984A is a complete 10-bit, 170 MSPS, monolithic
analog interface optimized for capturing YPbPr video and RGB
graphics signals. Its 170 MSPS encode rate capability and full
power analog bandwidth of 300 MHz support all HDTV video
modes up to 1080p, as well as graphics resolutions up to UXGA
(1600 × 1200 at 60 Hz).
The AD9984A includes a 170 MHz triple ADC with an internal
reference, a PLL, and programmable gain, offset, and clamp
control. The user provides only a 1.8 V power supply and an
analog input. Three-state CMOS outputs can be powered from
1.8 V to 3.3 V.
The AD9984A on-chip PLL generates a sample clock from the
tri-level sync (for YPbPr video) or the horizontal sync (for RGB
graphics). Sample clock output frequencies range from 10 MHz
to 170 MHz. With internal coast generation, the PLL maintains
its output frequency in the absence of a sync input. A 32-step
sampling clock phase adjustment is provided. Output data,
sync, and clock phase relationships are maintained.
The auto-offset feature can be enabled to automatically restore
the signal reference levels and calibrate out any offset differences
between the three channels. The auto channel-to-channel gain-
matching feature can be enabled to minimize any gain
mismatches between the three channels.
The AD9984A also offers full sync processing for composite sync
and sync-on-green applications. A clamp signal is generated
internally or can be provided by the user through the CLAMP
input pin.
Fabricated in an advanced CMOS process, the AD9984A is
provided in a space-saving, Pb-free, 80-lead low profile quad
flat package (LQFP) or 64-lead lead frame chip scale package
(LFCSP) and is specified over the 0°C to 70°C temperature range.
AD9984A
Rev. 0 | Page 2 of 44
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Analog Interface Characteristics ................................................ 3
Absolute Maximum Ratings............................................................ 5
Explanation of Test Levels........................................................... 5
Thermal Resistance ...................................................................... 5
ESD Caution.................................................................................. 5
Pin Configurations and Function Descriptions ........................... 6
Theory of Operation ...................................................................... 11
Digital Inputs .............................................................................. 11
Analog Input Signal Handling.................................................. 11
Hsync and Vsync Inputs............................................................ 11
Serial Control Port ..................................................................... 11
Output Signal Handling............................................................. 11
Clamping ..................................................................................... 11
Gain and Offset Control ............................................................ 12
Sync-on-Green............................................................................ 13
Reference Bypassing................................................................... 13
Clock Generation ....................................................................... 14
Sync Processing........................................................................... 16
Power Management.................................................................... 19
Timing Diagrams........................................................................ 19
Hsync Timing ............................................................................. 20
Coast Timing............................................................................... 21
Output Formatter ....................................................................... 21
2-Wire Serial Control Port ............................................................ 22
Data Transfer via Serial Interface............................................. 22
2-Wire Serial Register Map ........................................................... 24
2-Wire Serial Control Registers.................................................... 30
Chip Identification ..................................................................... 30
PLL Divider Control .................................................................. 30
Clock Generator Control .......................................................... 30
Phase Adjust................................................................................ 30
Input Gain ................................................................................... 30
Input Offset ................................................................................. 31
Hsync Control............................................................................. 31
Vsync Control............................................................................. 32
Coast and Clamp Controls........................................................ 33
SOG Control ............................................................................... 34
Input and Power Control........................................................... 35
Output Control........................................................................... 35
Sync Processing .......................................................................... 36
Detection Status.......................................................................... 37
Polarity Status ............................................................................. 37
Hsync Count ............................................................................... 38
Test Registers............................................................................... 38
PCB Layout Recommendations.................................................... 40
Analog Interface Inputs............................................................. 40
Outputs (Both Data and Clocks).............................................. 40
Digital Inputs .............................................................................. 41
Outline Dimensions ....................................................................... 42
Ordering Guide .......................................................................... 42
REVISION HISTORY
7/07—Revision 0: Initial Version
AD9984A
Rev. 0 | Page 3 of 44
SPECIFICATIONS
ANALOG INTERFACE CHARACTERISTICS
VD = 1.8 V, VDD = 3.3 V, PVD = 1.8 V, DAVDD = 1.8 V, ADC clock = maximum conversion rate, full temperature range = 0°C to 70°C.
Table 1. Electrical Characteristics
AD9984AKSTZ-140
AD9984AKCPZ-140
AD9984AKSTZ-170
AD9984AKCPZ-170
Parameter Temp
Test
Level1Min Typ Max Min Typ Max Unit
RESOLUTION
Number of Bits 10 10 Bits
LSB Size 0.098 0.098 % of full scale (FS)
DC ACCURACY
Differential Nonlinearity 25°C I ±0.6 +1.8/−1.0 ±0.7 +1.9/−1.0 LSB
Full VI +1.9/−1.0 +2.0/−1.0 LSB
Integral Nonlinearity 25°C I ±2.35 ±7.0 ±2.35 ±8.5 LSB
Full VI ±9.0 ±9.0 LSB
No Missing Codes Full VI GNT2 GNT2
ANALOG INPUT
Input Voltage Range
Minimum Full VI 0.5 0.5 V p-p
Maximum Full VI 1.0 1.0 V p-p
Gain Tempco 25°C V 125 125 ppm/°C
Input Bias Current 25°C IV 1 1 μA
Full IV 1 1 μA
Input Full-Scale Matching Full VI 1 1 % FS
Offset Adjustment Range Full VI 50 50 % FS
SWITCHING PERFORMANCE
Maximum Conversion Rate Full VI 140 170 MSPS
Minimum Conversion Rate Full IV 10 10 MSPS
Clock to Data Skew (tSKEW) Full IV −0.5 +2.0 −0.5 +2.0 ns
tBUFF Full VI 4.7 4.7 μs
tSTAH Full VI 4.0 4.0 μs
tDHO Full VI 0 0 μs
tDAL Full VI 4.7 4.7 μs
tDAH Full VI 4.0 4.0 μs
tDSU Full VI 250 250 ns
tSTASU Full VI 4.7 4.7 μs
tSTOSU Full VI 4.0 4.0 μs
Maximum PLL Clock Rate Full VI 140 170 MHz
Minimum PLL Clock Rate Full IV 10 10 MHz
Sampling Phase Tempco Full IV 15 15 ps/°C
DIGITAL INPUTS
Input Voltage, High (VIH) Full VI 1.0 1.0 V
Input Voltage, Low (VIL) Full VI 0.8 0.8 V
Input Current, High (IIH) Full V −1.0 −1.0 μA
Input Current, Low (IIL) Full V 1.0 1.0 μA
Input Capacitance 25°C V 2 2 pF
DIGITAL OUTPUTS
Output Voltage, High (VOH) Full VI VDD − 0.1 VDD − 0.1 V
Output Voltage, Low (VOL) Full VI 0.1 0.1 V
Duty Cycle (DATACK) Full IV 45 50 55 45 50 55 %
Output Coding Binary Binary
AD9984A
Rev. 0 | Page 4 of 44
AD9984AKSTZ-140
AD9984AKCPZ-140
AD9984AKSTZ-170
AD9984AKCPZ-170
Parameter Temp
Test
Level1Min Typ Max Min Typ Max Unit
POWER SUPPLY
VD Supply Voltage Full IV 1.7 1.8 1.9 1.755 1.8 1.9 V
VDD Supply Voltage Full IV 1.7 3.3 3.47 1.7 3.3 3.47 V
PVD Supply Voltage Full IV 1.7 1.8 1.9 1.7 1.8 1.9 V
DAVDD Supply Voltage Full IV 1.7 1.8 1.9 1.7 1.8 1.9 V
VD Supply Current (ID) 25°C V 250 255 mA
VDD Supply Current (IDD) 25°C V 31 34 mA
PVD Supply Current (IPVD) 25°C V 9 9 mA
DAVDD Supply Current (IDAVDD) 25°C V 16 19 mA
Total Power Dissipation Full VI 710 740 mW
Power-Down Supply Current Full VI 10 10 mA
Power-Down Dissipation Full VI 18 18 mW
DYNAMIC PERFORMANCE
Analog Bandwidth, Full Power 25°C V 300 300 MHz
Crosstalk Full V 60 60 dBc
1 See the Explanation of Test Levels section.
2 Guaranteed by design, not production tested.
AD9984A
Rev. 0 | Page 5 of 44
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
VD1.98 V
VDD 3.6 V
PVD1.98 V
DAVDD 1.98 V
Analog Inputs VD to 0.0 V
REFHI VD to 0.0 V
REFLO VD to 0.0 V
Digital Inputs 5 V to 0.0 V
Digital Output Current 20 mA
Operating Temperature Range −25°C to +85°C
Storage Temperature Range −65°C to +150°C
Maximum Junction Temperature 150°C
Maximum Case Temperature 150°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
EXPLANATION OF TEST LEVELS
I. 100% production tested.
II. 100% production tested at 25°C and sample tested at
specified temperatures.
III. Sample tested only.
IV. Parameter is guaranteed by design and characterization
testing.
V. Parameter is a typical value only.
VI. 100% production tested at 25°C; guaranteed by design
and characterization testing.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 3. Thermal Resistance
Package Type θJA θJC Unit
80-Lead LQFP 35 16 °C/W
64-Lead LFCSP 35 16 °C/W
ESD CAUTION
AD9984A
Rev. 0 | Page 6 of 44
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
2
B
AIN0
3
GND
4
B
AIN1
7
GND
6
G
AIN0
5
V
D
(1.8V)
1
V
D
(1.8V)
8
SOGIN0
9
V
D
(1.8V)
10
G
AIN1
12
SOGIN1
13
V
D
(1.8V)
14
R
AIN0
15
GND
16
R
AIN1
17
PWRDN
18
REFLO
19
NC
20
REFHI
11
GND
59
58
57
54
55
56
60
53
52
BLUE 4
BLUE 5
BLUE 6
BLUE 9
BLUE 8
BLUE 7
BLUE 3
GND
V
DD
(3.3V)
51
GREEN 0
49
GREEN 2
48
GREEN 3
47
GREEN 4
46
GREEN 5
45
GREEN 6
44
GREEN 7
43
GREEN 8
42
GREEN 9
41
DAV
DD
(1.8V)
50
GREEN 1
21
O/E FIELD
22
VSOUT/A0
23
HSOUT
24
SOGOUT
25
DATACK
26
V
DD
(3.3V)
27
GND
28
RED 9
29
RED 8
30
RED 7
31
RED 6
32
RED 5
33
RED 4
34
RED 3
35
RED 2
36
RED 1
37
RED 0
38
V
DD
(3.3V)
39
GND
40
GND
80
GND
79
PV
D
(1.8V)
78
FILT
77
GND
76
PV
D
(1.8V)
75
GND
74
PV
D
(1.8V)
73
CLAMP
72
EXTCK/COAST
71
VSYNC0
70
HSYNC0
69
VSYNC1
68
HSYNC1
67
SCL
66
SDA
65
GND
64
V
DD
(3.3V)
63
BLUE 0
62
BLUE 1
61
BLUE 2
AD9984A
TOP VIEW
(Not to Scale)
06476-002
NC = NO CONNECT
PIN 1
INDICATOR
Figure 2. 80-Lead LQFP Pin Configuration
AD9984A
Rev. 0 | Page 7 of 44
0
6476-020
16
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
3217 18 19 20 21 22 23 24 25 26 27 28 29 30 31
33
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
49
64 63 62 61 60 59 58 57 56 55 54 53 52 51 50
GREEN 7
GREEN 8
GREEN 9
GREEN 6
GREEN 5
GREEN 4
GREEN 3
GREEN 2
GREEN 1
GREEN 0
BLUE 9
BLUE 8
BLUE 4
BLUE 5
BLUE 6
BLUE 7
BLUE 3
BLUE 2
BLUE 1
BLUE 0
V
DD
SDA
SCL
HSYNC1
VSYNC1
HSYNC0
VSYNC0
EXTCK/COAST
PV
D
FILT
PV
D
CLAMP
O/E FIELD
REFHI
REFLO
PWRDN
R
AIN1
R
AIN0
V
D
SOGIN1
G
AIN1
V
D
SOGIN0
G
AIN0
V
D
B
AIN0
B
AIN1
V
D
DAV
DD
RED 2
RED 1
RED 0
RED 3
RED 4
RED 5
RED 6
RED 7
RED 8
RED 9
V
DD
VSOUT/A0
HSOUT
SOGOUT
DATACK
AD9984A
TOP VIEW
(Not to Scale)
29
PIN 1
INDICATOR
Figure 3. 64-Lead LFCSP Pin Configuration
Table 4. Complete Pin Configuration List
Pin Number
Pin Type 80-Lead LQFP 64-Lead LFCSP Mnemonic Function Value
Inputs 14 43 RAIN0 Channel 0 Analog Input for Converter R 0.0 V to 1.0 V
16 44 RAIN1 Channel 1 Analog Input for Converter R 0.0 V to 1.0 V
6 37 GAIN0 Channel 0 Analog Input for Converter G 0.0 V to 1.0 V
10 40 GAIN1 Channel 1 Analog Input for Converter G 0.0 V to 1.0 V
2 34 BBAIN0 Channel 0 Analog Input for Converter B 0.0 V to 1.0 V
4 35 BBAIN1 Channel 1 Analog Input for Converter B 0.0 V to 1.0 V
70 26 HSYNC0 Horizontal Sync Input for Channel 0 3.3 V CMOS
68 24 HSYNC1 Horizontal Sync Input for Channel 1 3.3 V CMOS
71 27 VSYNC0 Vertical Sync Input for Channel 0 3.3 V CMOS
69 25 VSYNC1 Vertical Sync Input for Channel 1 3.3 V CMOS
8 38 SOGIN0 Input for Sync-on-Green Channel 0 0.0 V to 1.0 V
12 41 SOGIN1 Input for Sync-on-Green Channel 1 0.0 V to 1.0 V
72 28 EXTCK1External Clock Input 3.3 V CMOS
73 29 CLAMP External Clamp Input Signal 3.3 V CMOS
72 28 COAST1External PLL Coast Signal Input 3.3 V CMOS
17 45 PWRDN Power-Down Control 3.3 V CMOS
AD9984A
Rev. 0 | Page 8 of 44
Pin Number
Pin Type 80-Lead LQFP 64-Lead LFCSP Mnemonic Function Value
Outputs 28 to 37 54 to 63 RED[9:0] Outputs of Converter R; Bit 9 is the MSB 3.3 V CMOS
42 to 51 1 to 10 GREEN[9:0] Outputs of Converter G; Bit 9 is the MSB 3.3 V CMOS
54 to 63 11 to 20 BLUE[9:0] Outputs of Converter B; Bit 9 is the MSB 3.3 V CMOS
25 52 DATACK Data Output Clock 3.3 V CMOS
23 50 HSOUT Hsync Output Clock (Phase-aligned with DATACK) 3.3 V CMOS
22 49 VSOUT2Vsync Output Clock 3.3 V CMOS
24 51 SOGOUT Sync-on-Green Slicer Output 3.3 V CMOS
21 48 O/E FIELD Odd/Even Field Output 3.3 V CMOS
References 78 31 FILT Connection for External Filter Components for Internal PLL
18 46 REFLO Connection for External Capacitor for Input Amplifier
20 47 REFHI Connection for External Capacitor for Input Amplifier
Power Supply 1, 5, 9, 13 33, 36, 39, 42 VDAnalog Power Supply 1.8 V
26, 38, 52, 64 21, 53 VDD Output Power Supply 1.8 V to 3.3 V
74, 76, 79 30, 32 PVDPLL Power Supply 1.8 V
41 64 DAVDD Digital Logic Power Supply 1.8 V
3, 7, 11, 15, 27,
39, 40, 53, 65,
75, 77, 80
N/A GND Ground 0 V
Control 66 22 SDA Serial Port Data I/O 3.3 V CMOS
67 23 SCL Serial Port Data Clock (100 kHz maximum) 3.3 V CMOS
22 49 A02Serial Port Address Input 3.3 V CMOS
1 EXTCK and COAST share the same pin.
2 VSOUT and A0 share the same pin.
AD9984A
Rev. 0 | Page 9 of 44
Table 5. Pin Function Descriptions
Mnemonic Function Description
RAIN0 Analog Input for the Red
Channel 0
GAIN0 Analog Input for the Green
Channel 0
BBAIN0 Analog Input for the Blue
Channel 0
RAIN1 Analog Input for the Red
Channel 1
GAIN1 Analog Input for the Green
Channel 1
BBAIN1 Analog Input for the Blue
Channel 1
These high impedance inputs accept the red, green, and blue channel graphics signals,
respectively. The three channels are identical and can be used for any colors, but colors
are assigned for convenient reference. They accommodate input signals ranging from
0.5 V to 1.0 V full scale. Signals should be ac-coupled to these pins to support clamp
operation. Refer to Figure 4 and Figure 5.
HSYNC0 Horizontal Sync Input
Channel 0
HSYNC1 Horizontal Sync Input
Channel 1
These inputs receive a logic signal that establishes the horizontal timing reference and
provides the frequency reference for pixel clock generation. The logic sense of these pins
can be automatically determined by the chip or manually controlled by Serial Register 0x12,
Bits[5:4] (Hsync polarity). Only the leading edge of Hsync is used by the PLL; the trailing
edge is used in clamp timing. When Hsync polarity = 0, the falling edge of Hsync is used.
When Hsync polarity = 1, the rising edge is active. These inputs include a Schmitt trigger
for noise immunity.
VSYNC0 Vertical Sync Input Channel 0
VSYNC1 Vertical Sync Input Channel 1
These inputs for vertical sync provide timing information for generation of the field
(odd/even) and internal coast generation. The logic sense of this pin can be
automatically determined by the chip or manually controlled by Serial Register 0x14,
Bits[5:4] (Vsync polarity).
SOGIN0 Sync-on-Green Input
Channel 0
SOGIN1 Sync-on-Green Input
Channel 1
These inputs help process signals with embedded sync, typically on the green channel.
These pins connect to a high speed comparator with an internally generated threshold.
The threshold level can be programmed in 8 mV steps to any voltage between 8 mV and
256 mV above the negative peak of the input signal. The default voltage threshold is
128 mV. When connected to an ac-coupled graphics signal with embedded sync, a
noninverting digital output is produced on SOGOUT. This output is usually a composite
sync signal, containing both vertical and horizontal sync information that must be
separated before passing the horizontal sync signal for Hsync processing. When not
used, these inputs should be left unconnected. For more details about this function and
how it should be configured, refer to the Sync-on-Green section.
CLAMP External Clamp Input
(Optional)
This logic input can be used to define the time during which the input signal is clamped
to ground or midscale. It should be exercised when the reference dc level is known to be
present on the analog input channels, typically during the back porch of the graphics
signal. The CLAMP pin is enabled by setting the control bit clamp function to 1, (Register 0x18,
Bit 4; default is 0). When disabled, this pin is ignored and the clamp timing is determined
internally by counting a delay and duration from the trailing edge of the Hsync input.
The logic sense of this pin can be automatically determined by the chip or controlled by
clamp polarity (Register 0x1B, Bits[7:6]). When not used, this pin can be left unconnected
(there is an internal pull-down resistor) and the clamp function programmed to 0.
EXTCK/COAST External Clock (EXTCK) This pin has dual functionality.
EXTCK allows the insertion of an external clock source rather than the internally
generated, PLL locked clock. EXTCK is enabled by programming Register 0x03, Bit 2 to 1.
This EXTCK function does not affect the COAST function.
Optional Coast Input to
Clock Generator (COAST)
COAST can be used to cause the pixel clock generator to stop synchronizing with Hsync
and continue to produce a clock at its current frequency and phase. This is useful when
processing signals from sources that fail to produce Hsync pulses during the vertical
interval. The coast signal is generally not required for PC-generated signals. The logic
sense of this pin can be determined automatically or controlled by coast polarity
(Register 0x18, Bits[7:6]). When this function and the EXTCK function are not used, this
pin can be grounded and coast polarity programmed to 1. Input coast polarity defaults
to 1 at power-up. This COAST function does not affect the EXTCK function.
PWRDN Power-Down Control
(PWRDN)
PWRDN allows for manual power-down control. If manual power-down control is selected
(Register 0x1E, Bit 4),and this pin is not used, it is recommended to set the pin polarity
(Register 0x1E, Bit 2) to active high and hardwire this pin to ground with a 10 kΩ resistor.
REFLO, REFHI Input Amplifier Reference REFLO and REFHI are connected together through a 10 μF capacitor. These are used for
stability in the input ADC circuitry. See Figure 6.
AD9984A
Rev. 0 | Page 10 of 44
Mnemonic Function Description
FILT External Filter Connection For proper operation, the pixel clock generator PLL requires an external filter. Connect the
filter shown in Figure 8 to this pin. For optimal performance, minimize noise and parasitics
on this node. For more information, see the PCB Layout Recommendations section.
HSOUT Horizontal Sync Output
This pin is a reconstructed and phase-aligned version of the Hsync input. Both the
polarity and duration of this output can be programmed via serial bus registers. By
maintaining alignment with DATACK and the main data outputs (RED[9:0], GREEN[9:0],
BLUE[9:0]), data timing with respect to Hsync can always be determined.
VSOUT/A0 Vertical Sync Output
(VSOUT)
This pin has dual functionality.
VSOUT can either be a separated Vsync from a composite signal or a direct pass through
of the Vsync signal. The polarity of this output can be controlled via a serial bus bit. The
placement and duration in all modes can be set by the graphics transmitter or the
duration can be set by Register 0x14, Bit 1 and Register 0x15, Bits[7:0]. This VSOUT function
does not affect the A0 function.
Serial Port Address Input 0
(A0)
A0 selects the LSB of the serial port device address, allowing two parts from Analog
Devices, Inc., to be on the same serial bus. A high impedance (10 kΩ), external pull-up
resistor enables this pin to be read at power-up as 1. This A0 function does not interfere
with the VSOUT function. For more details on A0, see the description in the 2-Wire Serial
Control Port section.
SOGOUT Sync-On-Green Slicer Output This pin outputs one of four possible signals (controlled by Register 0x1D, Bits[1:0]): raw
SOGINx, raw HSYNCx, regenerated Hsync from the filter, or the filtered Hsync. See Figure 9
to view how this pin is connected. Other than slicing off SOG, the output from this pin
receives no additional processing on the AD9984A. Vsync separation is performed via the
sync separator.
O/E FIELD Odd/Even Field Bit for
Interlaced Video
This output identifies whether the current field (in an interlaced signal) is odd or even.
SDA Serial Port Data I/O Data I/O for the I2C® serial port.
SCL Serial Port Data Clock Clock for the I2C serial port.
RED[9:0] Data Output, Red Channel
GREEN[9:0] Data Output, Green Channel
BLUE[9:0] Data Output, Blue Channel
The main data outputs. Bit 9 is the MSB. The delay from pixel sampling time to output is
fixed. When the sampling time is changed by adjusting the phase register, the output
timing is shifted as well. The DATACK and HSOUT outputs are also moved to maintain the
timing relationship among the signals.
DATACK Data Clock Output This is the main clock output signal used to strobe the output data and HSOUT into
external logic. Four possible output clocks can be selected with Register 0x20, Bits[7:6].
Three of these are related to the pixel clock (pixel clock, 90° phase-shifted pixel clock,
and 2× frequency pixel clock). They are produced by the internal PLL clock generator or
by EXTCK, and are synchronous with the pixel sampling clock. The fourth option for the
data clock output is an internally generated 0.5× pixel clock. The sampling time of the
internal pixel clock can be changed by adjusting the phase register (Register 0x04).
When this is changed, the pixel-related DATACK timing is also shifted. The data (RED[9:0],
GREEN[9:0], BLUE[9:0]), DATACK, and HSOUT outputs are moved to maintain the timing
relationship among the signals.
VD (1.8 V) Main Power Supply These pins supply power to the main elements of the circuit. They should be as quiet
and as filtered as possible.
VDD (1.8 V to 3.3 V) Digital Output Power Supply A large number of output pins (up to 35) switching at high speed (up to 170 MHz) generates
large amounts of power supply transients (noise). These supply pins are identified separately
from the VD pins. As a result, special care must be taken to minimize output noise transferred
into the sensitive analog circuitry. If the AD9984A is interfacing with lower voltage logic,
VDD can be connected to a lower supply voltage (as low as 1.8 V) for compatibility.
PVD (1.8 V) Clock Generator Power
Supply
The most sensitive portion of the AD9984A is the clock generation circuitry. These pins
provide power to the clock PLL and help the user design for optimal performance. The
designer should provide quiet, noise-free power to these pins.
DAVDD (1.8 V) Digital Input Power Supply This supplies power to the digital logic. It is recommended to connect this pin to
the VD supply.
GND Ground The ground return for all on-chip circuitry. It is recommended that the AD9984A be
assembled on a single solid ground plane with careful attention to ground current paths.
AD9984A
Rev. 0 | Page 11 of 44
THEORY OF OPERATION
The AD9984A is a fully integrated solution for capturing and
digitizing analog RGB or YPbPr signals for display on advanced
TVs, flat panel monitors, projectors, and other types of digital
displays. Implemented in a high performance CMOS process,
the interface can capture signals with pixel rates up to 170 MHz.
The AD9984A includes all necessary input buffering, signal dc
restoration (clamping), offset and gain (brightness and contrast)
adjustment, pixel clock generation, sampling phase control, and
output data formatting. All controls are programmable via a
2-wire serial interface (I2C). Full integration of these sensitive
analog functions makes system design straightforward and less
sensitive to the physical and electrical environment.
With a typical power dissipation of less than 900 mW and an
operating temperature range of 0°C to 70°C, the device requires
no special environmental considerations.
DIGITAL INPUTS
All digital inputs on the AD9984A operate to 3.3 V CMOS levels.
The following digital inputs are 5 V tolerant (that is, applying
5 V to them does not cause any damage): HSYNC0, HSYNC1,
VSYNC0, VSYNC1, SOGIN0, SOGIN1, SDA, SCL, and CLAMP.
ANALOG INPUT SIGNAL HANDLING
The AD9984A has six, high impedance, analog input pins for
the red, green, and blue channels. They accommodate signals
ranging from 0.5 V to 1.0 V p-p.
Signals are typically brought onto the interface board with a
DVI-I connector, a 15-pin D connector, or RCA connectors.
The AD9984A should be located as close as possible to the
input connector. Signals should be routed using matched-
impedance traces (normally 75 Ω) to the IC input pins.
At the input pins, the signal should be resistively terminated
(75 Ω to the signal ground return) and capacitively coupled to
the AD9984A inputs through 47 nF capacitors. These capacitors
form part of the dc restoration circuit.
In an ideal world of perfectly matched impedances, the best
performance can be obtained with the widest possible signal
bandwidth. The wide bandwidth inputs of the AD9984A
(300 MHz) can track the input signal continuously as it moves
from one pixel level to the next and can digitize the pixel during
a long, flat pixel time. In many systems, however, there are
mismatches, reflections, and noise, which can result in excessive
ringing and distortion of the input waveform. This makes it
more difficult to establish a sampling phase that provides good
image quality. A small inductor in series with the input is shown
to be effective in rolling off the input bandwidth slightly and
providing a high quality signal over a wider range of conditions.
Using a high speed, signal chip, bead inductor (such as the
Fair-Rite 2508051217Z0) in the circuit shown in Figure 4
provides good results in most applications.
RGB
INPUT
RAIN
GAIN
BAIN
75Ω
06476-003
47n
F
Figure 4. Analog Input Interface Circuit
HSYNC AND VSYNC INPUTS
The interface also accepts Hsync and Vsync signals, which are
used to generate the pixel clock, clamp timing, and coast and
field information. These can be either a sync signal directly
from the graphics source, or a preprocessed TTL- or CMOS-
level signal.
The Hsync input includes a Schmitt trigger buffer for immunity
to noise and signals with long rise times. In typical PC-based
graphic systems, the sync signals are simply TTL-level drivers
feeding unshielded wires into the monitor cable. As such, no
termination is required.
SERIAL CONTROL PORT
The serial control port is designed for 3.3 V logic; however, it is
tolerant of 5 V logic signals. Refer to the 2-Wire Serial Control
Port section for more information.
OUTPUT SIGNAL HANDLING
The digital outputs operate from 1.8 V to 3.3 V (VDD).
CLAMPING
RGB Clamping
To properly digitize the incoming signal, the dc offset of the
input must be adjusted to fit the range of the on-board ADCs.
Most graphics systems produce RGB signals with black at
ground and white at approximately 0.75 V. However, if sync
signals are embedded in the graphics, the sync tip is often at
ground, black is at 300 mV, and white is at approximately 1.0 V.
Some common RGB line amplifier boxes use emitter-follower
buffers to split signals and increase drive capability. This
introduces a 700 mV dc offset to the signal, which must be
removed for proper capture by the AD9984A.
The key to clamping is to identify a portion (time) of the signal
when the graphic system is known to be producing black. An
offset is then introduced that results in the ADC producing a
black output (Code 0x00) when the known black input is present.
The offset then remains in place when other signal levels are
processed, and the entire signal is shifted to eliminate offset errors.
In most PC graphics systems, black is transmitted between
active video lines. With CRT displays, when the electron beam
has completed writing a horizontal line on the screen (at the
right side), the beam is deflected quickly to the left side of the
screen (called horizontal retrace) and a black signal is provided
to prevent the beam from disturbing the image.
AD9984A
Rev. 0 | Page 12 of 44
In systems with embedded sync, a blacker-than-black signal
(Hsync) is briefly produced to signal the CRT that it is time to
begin a retrace. Because the input is not at black level at this
time, it is important to avoid clamping during Hsync. Fortunately,
there is usually a period following Hsync (called the back porch)
where a good black reference is provided. This is the time when
clamping should be done.
The clamp timing can be established by simply exercising
the CLAMP pin at the appropriate time with clamp source
(Register 0x18, Bit 4) = 1. The polarity of this signal is set by
the clamp polarity bits (Register 0x1B, Bits[7:6]).
A simpler method of clamp timing employs the AD9984A
internal clamp timing generator. The clamp placement register
(Register 0x19) is programmed with the number of pixel periods
that should pass after the trailing edge of Hsync before clamping
starts. A second register, clamp duration (Register 0x1A), sets
the duration of the clamp. These are both 8-bit values, providing
considerable flexibility in clamp generation. Although Hsync
duration can widely vary, the clamp timing is referenced to the
trailing edge of Hsync because the back porch (black reference)
always follows Hsync. An effective starting point for establishing
clamping is to set the clamp placement to 0x04 (providing 4 pixel
periods for the graphics signal to stabilize after sync) and set the
clamp duration to 0x28 (giving the clamp 40 pixel periods to
reestablish the black reference).
Clamping is accomplished by placing an appropriate charge on
the external input coupling capacitor. The value of this capacitor
affects the performance of the clamp. If it is too small, there is a
significant amplitude change during a horizontal line time
(between clamping intervals). If the capacitor is too large, it
takes a long time for the clamp to recover from a large change
in incoming signal offset. The recommended value (100 nF)
results in recovering from a step error of 100 mV to within 1 LSB
in 60 lines with a clamp duration of 20 pixel periods on a 85 Hz
XGA signal.
YPbPr Clamping
YPbPr graphic signals are slightly different from RGB signals in
that the dc reference level (black level in RGB signals) of color
difference signals is at the midpoint of the video signal rather than
at the bottom. The three inputs are composed of luminance (Y)
and color difference (Pb and Pr) signals. For color difference
signals, it is necessary to clamp to the midscale range of the
ADC range (512) rather than to the bottom of the ADC range (0),
while the Y channel is clamped to ground.
Clamping to midscale rather than ground can be accomplished
by setting the clamp select bits in the serial bus register. Each of
the three converters has its own selection bit to enable them to
be independently clamped to midscale or ground. These bits are
located in Register 0x18, Bits[3:1]. The midscale reference
voltage is internally generated for each converter.
GAIN AND OFFSET CONTROL
The AD9984A contains three programmable gain amplifiers
(PGAs), one for each of the three analog inputs. The range of
the PGA is sufficient to accommodate input signals with inputs
ranging from 0.5 V to 1.0 V full scale. The gain is set in three
9-bit registers, red gain (Register 0x05, Register 0x06), green
gain (Register 0x07, Register 0x08), and blue gain (Register 0x09,
Register 0x0A). For each register, a gain setting of 0d corresponds
to the highest gain, while a gain setting of 511d corresponds to
the lowest gain. Note that increasing the gain setting results in
an image with less contrast.
The offset control shifts the analog input, resulting in a change
in brightness. Three 11-bit registers, red offset (Register 0x0B,
Register 0x0C), green offset (Register 0x0D, Register 0x0E),
and blue offset (Register 0x0F, Register 0x10) provide inde-
pendent settings for each channel. Note that the function of
the offset register depends on whether auto-offset is enabled
(Register 0x1B, Bit 5).
If manual offset is used, nine bits of the offset registers (for the
red channel, Register 0x0B, Bits[6:0] plus Register 0x0C, Bits[7:6])
control the absolute offset added to the channel. The offset control
provides ±255 LSBs of adjustment range, with 1 LSB of offset
corresponding to 1 LSB of output code.
Automatic Offset
In addition to the manual offset adjustment mode, the AD9984A
also includes circuitry to automatically calibrate the offset for
each channel. By monitoring the output of each ADC during
the back porch of the input signals, the AD9984A can self-adjust
to eliminate any offset errors in its own ADC channels and any
offset errors present on the incoming graphics or video signals.
To activate the auto-offset mode, set Register 0x1B, Bit 5 to 1. Next,
the target code registers (Register 0x0B through Register 0x10)
must be programmed. The values programmed into the target
code registers should be the output code desired from the
AD9984A during the back porch reference time.
For example, for RGB signals, all three registers are normally
programmed to Code 2, while for YPbPr signals, the green
(Y) channel is normally programmed to Code 2, and the blue
and red channels (Pb and Pr) are normally set to 512. The
target code registers have 11 bits per channel and are in twos
complement format. This allows any value between −1024 and
+1023 to be programmed. Although any value in this range can
be programmed, the AD9984A offset range may not be able to
reach every value. Intended target code values range from (but
are not limited to) −160 to −1 and +1 to +160 when ground
clamping, and 350 to 670 when midscale clamping. Note that a
target code of 0 is not valid.
AD9984A
Rev. 0 | Page 13 of 44
Negative target codes are included to duplicate a feature that is
present with manual offset adjustment. The benefit that is
mimicked is the ability to easily adjust brightness on a display. By
setting the target code to a value that does not correspond to the
ideal ADC range, the end result is an image that is brighter or
darker. A target code higher than ideal results in a brighter image,
whereas a target code lower than ideal results in a darker image.
The ability to program a target code offers a large degree of
freedom and flexibility. Although all channels are set to either 1
or 512 in most cases, the flexibility to select other values makes
it possible to insert intentional skews between channels. It also
allows the ADC range to be skewed so that voltages outside of
the normal range can be digitized. For example, setting the
target code to 40 allows the sync tip, which is normally below
black level, to be digitized and evaluated.
The internal logic for the auto-offset circuit requires 16 data
clock cycles to perform its function. This operation is executed
immediately after the clamping pulse. Therefore, it is important
to end the clamping pulse signal at least 16 data clock cycles
before active video. This is true whether using the AD9984A
internal clamp circuit or an external CLAMP signal. The auto-
offset function can be programmed to run continuously or on a
one-time basis (see the 0x2C—Bit[4] Auto-Offset Hold
section). In continuous mode, the update frequency can be
programmed (Register 0x1B, Bits[4:3]). Continuous operation
with updates every 192 Hsyncs is recommended.
Guidelines for basic auto-offset operation are shown in Tabl e 6
and Table 7.
Table 6. RGB Auto-Offset Register Settings
Register Value Comments
0x0B 0x00 Sets red target to 4.
0x0C 0x80 Must be written.
0x0D 0x00 Sets green target to 4.
0x0E 0x80 Must be written.
0x0F 0x00 Sets blue target to 4.
0x10 0x80 Must be written.
0x18, Bits[3:1] 000 Sets red, green, and blue channels to
ground clamp.
0x1B, Bits[5:3] 110 Selects update rate to every 192
clamps and enables auto-offset.
Table 7. YPbPr Auto-Offset Register Settings
Register Value Comments
0x0B 0x40 Sets Pr (red) target to 512.
0x0C 0x00 Must be written.
0x0D 0x00 Sets Y (green) target to 4.
0x0E 0x80 Must be written.
0x0F 0x40 Sets Pb (blue) target to 512.
0x10 0x00 Must be written.
0x18, Bits[3:1] 101 Sets Pb, Pr to midscale clamp and Y to
ground clamp.
0x1B, Bits[5:3] 110 Selects update rate to every 192
clamps and enables auto-offset.
Automatic Gain Matching
The AD9984A includes circuitry to match the gains between
the three channels to within 1% of each other. Matching the
gains of each channel is necessary to achieve good color balance
on a display. On products without this feature, gain matching is
achieved by writing software that evaluates the output of each
channel, calculates gain mismatches, and then writes values to
the gain registers of each channel to compensate. With the auto
gain matching function, this software routine is no longer needed.
To activate auto gain matching, set Register 0x3C, Bits[2:0] to 110.
Auto gain matching has similar timing requirements to auto
offset. It requires 16 data clock cycles to perform its function,
starting immediately after the end of the clamp pulse. Unlike
auto offset, auto gain matching does not require that these
16 clock cycles occur during the back porch reference time,
although it is recommended. During auto gain matching
operation, the data outputs of the AD9984A are frozen (held at
the value they had just prior to operation). The auto gain
matching function can be programmed to run continuously or
on a one-time basis (see the 0x3C—Bit[3] Auto Gain Matching
Hold section). In continuous mode, the update frequency can
be programmed (Register 0x1B, Bits[4:3]). Continuous
operation with updates every 192 Hsyncs is recommended.
SYNC-ON-GREEN
The sync-on-green inputs (SOGIN0, SOGIN1) operate in two
steps. First, they set a baseline clamp level off the incoming
video signal with a negative peak detector. Second, they set the
voltage level of the SOG slicer’s comparator (Register 0x1D,
Bits[7:3]) with a variable trigger level to a programmable level
(typically 128 mV) above the negative peak. Each sync-on-
green input must be ac-coupled to the green analog input
through its own capacitor. The value of the capacitor must be
1 nF ± 20%. If sync-on-green is not used, this connection is not
required. The sync-on-green signal always has negative polarity.
R
AIN
B
AIN
G
AIN
SOGIN
47nF
47nF
47nF
1nF
0
6476-004
Figure 5. Typical Input Configuration
REFERENCE BYPASSING
REFLO and REFHI are connected to each other by a 10 μF
capacitor (see Figure 6). These references are used by the input
ADC circuitry.
REFHI
REFLO
10µF
0
6476-005
Figure 6. Input Amplifier Reference Capacitors
AD9984A
Rev. 0 | Page 14 of 44
CLOCK GENERATION
A PLL is used to generate the pixel clock. The Hsync input
provides a reference frequency to the PLL. A voltage controlled
oscillator (VCO) generates a much higher pixel clock frequency.
The pixel clock is divided by the PLL divide value (Register 0x01
and Register 0x02) and phase-compared with the Hsync input.
Any error is used to shift the VCO frequency and maintain lock
between the two signals.
The stability of this clock is a very important element in provid-
ing the clearest and most stable image. During each pixel time,
the signal slews from the old pixel amplitude and settles at its
new value; this is called the slewing time. Then, the input voltage
stabilizes before the signal must slew to a new value; this is called
the stable time. The ratio of the slewing time to the stable time is
a function of the graphics DAC bandwidth and the bandwidth
of the transmission system (cable and termination). This ratio is
also a function of the overall pixel rate. If the dynamic charac-
teristics of the system remain fixed, the slewing and settling
time is likewise fixed. This time must be subtracted from the
total pixel period, leaving the stable period. At higher pixel
frequencies, the total cycle time is shorter and the stable pixel
time becomes shorter as well.
PIXEL CLOC
K
IN
V
ALID SAMPLE TIMES
0
6476-006
Figure 7. Pixel Sampling Times
Any jitter in the clock reduces the precision of the sampling
time and it must also be subtracted from the stable pixel time.
Considerable care has been taken in the design of the AD9984A
clock generation circuit to minimize jitter. The clock jitter of the
AD9984A is low in all operating modes, making the reduction
in the valid sampling time due to jitter negligible.
The PLL characteristics are determined by the loop filter design,
the PLL charge pump current, and the VCO range setting. The
loop filter design is illustrated in Figure 8. Recommended settings
of the VCO range and charge pump current for VESA standard
display modes are listed in Table 10.
C
P
8.2n
F
C
Z
82nF
R
Z
1.5kΩ
FILT
PV
D
06476-007
Figure 8. PLL Loop Filter Design
Four programmable registers are provided to optimize the
performance of the PLL. These registers are the 12-bit divisor
register, the 2-bit VCO range register, the 3-bit charge pump
current register, and the 5-bit phase adjust register.
The 12-Bit Divisor Register
The input Hsync frequencies can accommodate any Hsync as
long as the product of the Hsync and the PLL divisor falls
within the operating range of the VCO. The PLL multiplies the
frequency of the Hsync signal, producing pixel clock frequencies
in the range of 10 MHz to 170 MHz. The divisor register controls
the exact multiplication factor. This register can be set to any
value between 2 and 4095 as long as the output frequency is
within range.
The 2-Bit VCO Range Register
To improve the noise performance of the AD9984A, the VCO
operating frequency range is divided into four overlapping
regions. The VCO range register sets this operating range. The
frequency ranges for the four regions are shown in Table 8 .
Table 8. VCO Frequency Ranges
PV1 PV0 Pixel Clock Range (MHz) KVCO Gain (MHz/V)
0 0 10 to 311150
0 1 31 to 62 150
1 0 62 to 124 150
1 1 124 to 170 150
1 For frequencies of 18 MHz or lower, enable the VCO low range bit (Reg. 0x36[0]).
The 3-Bit Charge Pump Current Register
This register varies the current that drives the low-pass loop
filter. The possible current values are listed in Table 9.
Table 9. Charge Pump Current/Control Bits
Ip2 Ip1 Ip0 Current (μA)
0 0 0 50
0 0 1 100
0 1 0 150
0 1 1 250
1 0 0 350
1 0 1 500
1 1 0 750
1 1 1 1500
The 5-Bit Phase Adjust Register
The phase of the generated sampling clock can be shifted to
locate an optimum sampling point within a clock cycle. The
phase adjust register provides 32 phase-shift steps of 11.25°
each. The Hsync signal with an identical phase shift is available
through the HSOUT pin. Phase adjust is still available if an
external pixel clock is used. The COAST pin or the internal
coast is used to allow the PLL to continue to run at the same
frequency in the absence of the incoming Hsync signal or
during disturbances in Hsync (such as from equalization
pulses). This can be used during the vertical sync period or at
any other time that the Hsync signal is unavailable.
AD9984A
Rev. 0 | Page 15 of 44
The polarity of the coast signal can be set through the coast
polarity register (Register 0x18, Bits[6:5]). In addition, the
polarity of the Hsync signal can be set through the Hsync polarity
register (Register 0x12, Bits[5:4]). For both Hsync and coast,
a value of 1 is active high. The internal coast function is driven
off the Vsync signal, which is typically a time when Hsync
signals can be disrupted with extra equalization pulses.
Table 10. Recommended VCO Range and Charge Pump and Current Settings for Standard Display Formats
Standard Resolution
Refresh
Rate (Hz)
Horizontal
Frequency (kHz)
Pixel Rate
(MHz)
PLL
Divider
VCO
Range Current
VCO Gear
(Reg.0x36[0])
VGA 640 × 480 60 31.500 25.175 800 00 101 0
72 37.700 31.500 832 01 100 0
75 37.500 31.500 840 01 100 0
85 43.300 36.000 832 01 100 0
SVGA 800 × 600 56 35.100 36.000 1024 01 100 0
60 37.900 40.000 1056 01 101 0
72 48.100 50.000 1040 01 101 0
75 46.900 49.500 1056 01 101 0
85 53.700 56.250 1048 01 110 0
XGA 1024 × 768 60 48.400 65.000 1344 10 100 0
70 56.500 75.000 1328 10 101 0
75 60.000 78.750 1312 10 101 0
80 64.000 85.500 1336 10 101 0
85 68.300 94.500 1376 10 110 0
SXGA 1280 × 1024 60 64.000 108.000 1688 10 110 0
75 80.000 135.000 1688 11 110 0
85 91.100 157.500 1728 11 110 0
UXGA 1600 × 1200 60 75.000 162.000 2160 11 110 0
TV 480i 30 15.750 13.510 858 00 101 1
480p 60 31.470 27.000 858 00 101 0
576i 30 15.625 13.500 864 00 101 1
576p 60 31.250 27.000 864 00 101 0
720p 60 45.000 74.250 1650 10 101 0
1035i 30 33.750 74.250 2200 10 101 0
1080i 60 33.750 74.250 2200 10 101 0
1080p 60 67.500 148.500 2200 11 101 0
AD9984A
Rev. 0 | Page 16 of 44
SYNC PROCESSING
The inputs of the sync processing section of the AD9984A are
combinations of digital Hsyncs and Vsyncs, analog sync-on-
green or sync-on-Y signals, and an optional external coast
signal. From these signals, the part generates a precise, jitter-
free clock from its PLL, an odd/even-field signal, HSOUT and
VSOUT signals, a count of Hsyncs per Vsync, and a
programmable SOGOUT. The main sync processing blocks are
the sync slicer, sync separator, Hsync filter, Hsync regenerator,
Vsync filter, and coast generator.
• The sync slicer extracts the sync signal from the green
graphics or luminance video signal that is connected to
the SOGINx inputs, and outputs a digital composite sync.
• The sync separator extracts Vsync from the composite sync
signal, which can come from either the sync slicer or the
HSYNCx inputs.
• The Hsync filter is used to eliminate any extraneous pulses
from the HSYNCx or SOGINx inputs, outputting a clean,
low-jitter signal that is appropriate for mode detection and
clock generation.
• The Hsync regenerator is used to recreate a clean, although
not low jitter, Hsync signal that can be used for mode
detection and counting Hsyncs per Vsync.
• The Vsync filter is used to eliminate spurious Vsyncs, main-
tain a stable timing relationship between the Vsync and Hsync
output signals, and generate the odd/even field output.
• The coast generator creates a robust coast signal to allow the
PLL to maintain its frequency in the absence of Hsync pulses.
AD9984A
SOGOUT
HSYNC
VSYNC
COAST
COAST SELECT
0x18:7
DATACK
SOGIN0
EXTCK/COAST
VSYNC1
MUX
MUX
MUX
MUX MUX
MUX
MUX
MUX
VSYNC0
HSYNC1
HSYNC0
HSOUT
VSOUT/A0
SOGIN1
HSYNC
SELECT
0x12:6
FILTERED
HSYNC
ACTIVITY
DETECT
ACTIVITY
DETECT
ACTIVITY
DETECT
ACTIVITY
DETECT
ACTIVITY
DETECT
ACTIVITY
DETECT
POLARITY
DETECT
POLARITY
DETECT
POLARITY
DETECT
POLARITY
DETECT
SYNC SLICER
SYNC SLICER
PLL CLOCK
GENERATOR
O/E FIELD
CHANNEL
SELECT
0x1E:6
HSYNC FILTER
AND
REGENERATOR
REGENERATED
HSYNC
SET
POLARITY
SYNC PROCESSOR
AND VSYNC FILTER
06476-008
SET
POLARITY
HSYNC/VSYNC
COUNTER
REG 0x26,
0x27
SET
POLARITY
SET
POLARITY
VSYNC
FILTERED VSYNC
VSYNC FILTER EN
0x14:2
VSYNC
FILTER EN
0x14:2
PLL SYNC
FILTER EN
0x20:2
SP SYNC
FILTER EN
0x20:1
SOGOUT
SELECT
0x1D:1,0
MUX
Figure 9. Sync Processing Block Diagram
AD9984A
Rev. 0 | Page 17 of 44
Sync Slicer
The purpose of the sync slicer is to extract the sync signal from
the green graphics or luminance video signal that is connected
to the SOG input. The sync signal is extracted in a two step
process. First, the SOG input is clamped to its negative peak,
(typically 0.3 V below the black level). Next, the signal goes to a
comparator with a variable trigger level (set by Register 0x1D,
Bits[7:3]), but nominally 0.128 V above the clamped level. The
sync slicer output is a digital composite sync signal containing
both Hsync and Vsync information (see Figure 10).
Sync Separator
As part of sync processing, the sync separator’s task is to extract
Vsync from the composite sync signal. It works on the idea that
the Vsync signal stays active for a much longer time than the
Hsync signal. By using a digital low-pass filter and a digital
comparator, the sync separator rejects pulses with small
durations (such as Hsyncs and equalization pulses) and only
passes pulses with large durations, such as Vsync (see Figure 10).
The threshold of the digital comparator is programmable
for maximum flexibility. To program the threshold duration,
write a value (N) to Register 0x11. The resulting pulse width
is N × 200 ns. If, for example, N = 5, the digital comparator
threshold is 1 μs. Any pulse less than 1 μs is rejected, while any
pulse greater than 1 μs passes through.
There are two factors to keep in mind when using the sync
separator. First, the resulting clean Vsync output is delayed
from the original Vsync by a duration equal to the digital
comparator threshold (N × 200 ns). Second, there is some
variability to the 200 ns multiplier value. The maximum
variability over all operating conditions is ±20% (160 ns to
240 ns). Because normal Vsync and Hsync pulse widths differ
by a factor of approximately 500 or more, the 20% variability is
not an issue.
Hsync Filter and Regenerator
The Hsync filter is used to eliminate any extraneous pulses from
the Hsync or SOG inputs, outputting a clean, low jitter signal
that is appropriate for mode detection and clock generation.
The Hsync regenerator is used to recreate a clean, but not low
jitter, Hsync signal that can be used for mode detection and
counting Hsyncs per Vsync. The Hsync regenerator has a high
degree of tolerance to extraneous and missing pulses on the
Hsync input, but is not appropriate for use by the PLL in
creating the pixel clock due to jitter.
The Hsync regenerator runs automatically and requires no setup
to operate. The Hsync filter requires the setting up of a filter
window. The filter window sets a periodic window of time
around the regenerated Hsync leading edge where valid Hsyncs
are allowed to occur. The general idea is that extraneous pulses
on the sync input occur outside of this filter window and are
thus, filtered out. To set the filter window timing, program a
value (x) into Register 0x23. The resulting filter window time is
±x times 25 ns around the regenerated Hsync leading edge. Just
as for the sync separator threshold multiplier, allow a ±20%
variance in the 25 ns multiplier to account for all operating
conditions (20 ns to 30 ns range).
A second output from the Hsync filter is a status bit (Register 0x25,
Bit 1) that indicates if extraneous pulses are present on the
incoming sync signal. Extraneous pulses are often included for
copy protection purposes, so this status bit can be used to detect
such pulses.
The filtered Hsync (rather than the raw HSYNCx/SOGINx
signal) for pixel clock generation by the PLL is controlled by
Register 0x20, Bit 2. The regenerated Hsync (rather than
the raw HSYNCx/SOGINx signal) for the sync processing is
controlled by Register 0x20, Bit 1. Using the filtered Hsync
and regenerated Hsync is recommended. See Figure 11 for an
illustration of a filtered Hsync.
SOG INPUT
SOGOUT OUTPUT
CONNECTED TO
HSYNCIN
NEGATIVE PULSE WIDTH = 40 SAMPLE CLOCKS
COMPOSITE
SYNC
AT HSYNCIN
VSYNCOUT
FROM SYNC
SEPARATOR
–300mV
+300mV
700mV MAXIMUM
0mV
06476-009
Figure 10. Sync Slicer and Sync Separator Output
AD9984A
Rev. 0 | Page 18 of 44
HSYNCOUT
VSYNC
FILTER
WINDOW
EXPECTED
EDGE
FILTER
WINDOW
EQUALIZATION
PULSES
HSYNCIN
06476-010
Figure 11. Sync Processing Filter
Vsync Filter and Odd/Even Fields
The Vsync filter is used to eliminate spurious Vsyncs, maintain
a stable timing relationship between the Vsync and Hsync
output signals, and generate the odd/even field output.
The filter works by examining the placement of Vsync with
respect to Hsync and if necessary, shifting it in time slightly.
The goal is to keep the Vsync and Hsync leading edges from
switching at the same time, thus eliminating confusion as to
when the first line of a frame occurs. Register 0x14, Bit 2 enables
the Vsync filter. Use of the Vsync filter is recommended for all
cases, including interlaced video, and is required when using
the Hsyncs per Vsync counter. Figure 12 and Figure 13 illustrate
even/odd field determination in two situations.
FIELD 1 FIELD 0 FIELD 1 FIELD 0
23 214431
HSYNCIN
VSYNCIN
VSYNCOUT
O/E FIELD
EVEN FIELD
QUADRANT
06476-012
SYNC SEPERATOR THRESHOLD
Figure 12. Even Field
FIELD 1 FIELD 0 FIELD 1 FIELD 0
23 214431
HSYNCIN
VSYNCIN
VSYNCOUT
O/E FIELD
ODD FIELD
QUADRANT
06476-011
SYNC SEPERATOR THRESHOLD
Figure 13. Odd Field
AD9984A
Rev. 0 | Page 19 of 44
POWER MANAGEMENT
To meet display requirements for low standby power, the
AD9984A includes a power-down mode. The power-down state
can be controlled manually (via Pin 17 or Register 0x1E, Bit 3),
or automatically by the chip. If automatic control is selected
(Register 0x1E, Bit 4 =1), the AD9984A’s decision is based on
the status of the following sync detect bits in Register 0x24: Bit 2,
Bit 3, Bit 6, and Bit 7. If either an Hsync or a sync-on-green input
is detected on any input, the chip powers up; otherwise, it powers
down. For manual control, the AD9984A allows flexibility of
control through both a dedicated pin and a register bit. For the
dedicated pin, a hardware watchdog circuit controls power-down,
while software controls power-down for the register bit. With
manual power-down control, the polarity of the power-down
pin must be set (Register 0x1E, Bit 2) whether the pin is used or
not. If unused, it is recommended to set the polarity to active
high and hardwire the pin to ground with a 10 kΩ resistor.
In power-down mode, several circuits continue to operate
normally. The serial register and sync detect circuits maintain
power so that the AD9984A can be woken up from its power-
down state. The band gap circuit maintains power because it is
needed for sync detection. The sync-on-green and SOGOUT
functions continue to operate because SOGOUT is needed
when sync detection is performed by a secondary chip. All of
these circuits require minimal power to operate. Typical
standby power on the AD9984A is about 50 mW.
There are two options that can be selected when in power-
down. These are controlled by Bit 0 and Bit 1 in Register 0x1E.
Bit 0 controls whether the SOGOUT pin is in high impedance
or not. In most cases, the user does not place SOGOUT in high
impedance during normal operation. The option to put SOGOUT
in high impedance is included mainly to allow for factory testing
modes. Bit 1 keeps the AD9984A powered up while placing
only the outputs in high impedance. This option is useful when
the data outputs from two chips are connected on a PCB and
the user wants to switch instantaneously between the two.
Table 11.Power-Down Control and Mode Descriptions
Inputs
Mode Auto Power-Down Control1Power-Down2Sync Detect3Powered on/Comments
Power-Up 1 X 1 Everything.
Power-Down 1 X 0 Only the serial bus, sync activity detect,
SOG, band gap reference.
Power-Up 0 0 X Everything.
Power-Down 0 1 X Only the serial bus, sync activity detect,
SOG, band gap reference.
1 Auto power-down control is set by Register 0x1E, Bit 4.
2 Power-down is controlled by OR’ing Pin 17 with Register 0x1E, Bit 3. The polarity of Pin 17 is set by Register 0x1E, Bit 2.
3 Sync detect is determined by OR’ing Register 0x24, Bit 2, Bit 3, Bit 6, and Bit 7.
TIMING DIAGRAMS
The timing diagrams in Figure 14 to Figure 17 show the operation of the AD9984A. The output data clock signal is created so that its
rising edge always occurs between data transitions and can be used to latch the output data externally. There is a pipeline in the AD9984A
that must be flushed before valid data becomes available. This means six data sets are present before valid data is available.
t
PER
t
DCYCLE
t
SKEW
DATACK
DATA
HSOUT
06476-013
Figure 14. Output Timing
AD9984A
Rev. 0 | Page 20 of 44
DATAIN P0 P1 P2 P5P3 P4 P9P6 P8 P10 P11P7
HSYNCx
DATACK
8 CLOCK CYCLE DELAY
DATAOUT P0 P1 P2 P3
2 CLOCK CYCLE DELAY
HSOUT
06476-014
Figure 15. 4:4:4 Timing Mode
DATAIN
HSYNCx
DATACK
8 CLOCK CYCLE DELAY
Cb/CrOUT
YOUT
2 CLOCK CYCLE DELAY
HSOUT
NOTES
1. PIXEL AFTER HSOUT CORRESPONDS TO BLUE INPUT.
2. EVEN NUMBER OF PIXEL DELAY BETWEEN HSOUT AND DATAOUT.
P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11
Y0
CB0 CR0 CB2 CR2
Y1 Y2 Y3
06476-015
Figure 16. 4:2:2 Timing Mode
DATAIN P0 P1 P2 P5
P3 P4 P9P6 P8 P10 P11P7
HSYNCx
DATAC
K
8 CLOCK CYCLE DELAY
2 CLOCK CYCLE DELAY
DDR NOTES
1. OUTPUT DATACK MAY BE DELAYED 1/4 CLOCK PERIOD IN THE REGISTERS.
2. SEE PROJECT DOCUMENT FOR VALUES OF F (FALLING EDGE) AND R (RISING EDGE).
3. FOR DDR 4:2:2 MODE: TIMING IS IDENTICAL, VALUES OF F AND R CHANGE.
GENERAL NOTES
1. DATA DELAY MAY VARY ± ONE CLOCK CYCLE, DEPENDING ON PHASE SETTING.
2. ADCs SAMPLE INPUT ON FALLING EDGE OF DATACK.
3. HSYNC SHOWN IS ACTIVE HIGH (EDGE SHOWN IS LEADING EDGE).
HSOUT
F0 R0 F1 R1 F2 R2 F3 R3
06476-016
Figure 17. Double Data Rate (DDR) Timing Mode
HSYNC TIMING
The Hsync is processed in the AD9984A to eliminate ambiguity
in the timing of the leading edge with respect to the phase-
delayed pixel clock and data.
The Hsync input is used as a reference to generate the pixel
sampling clock. The sampling phase can be adjusted with
respect to Hsync through a full 360° in 32 steps via the phase
adjust register (to optimize the pixel sampling time). Display
systems use Hsync to align memory and display write cycles.
Therefore, it is important to have a stable timing relationship
between the Hsync output (HSOUT) and data clock (DATACK).
Three things happen to Hsync in the AD9984A. First, the
polarity of Hsync input is determined and, as a result, has a
known output polarity. The known output polarity can be
programmed either active high or active low (Register 0x12,
Bit 3). Second, HSOUT is aligned with DATACK and data
outputs. Third, the duration of HSOUT (in pixel clocks) is set
via Register 0x13. HSOUT is the sync signal that should be used
to drive the rest of the display system.
AD9984A
Rev. 0 | Page 21 of 44
COAST TIMING
In most computer systems, the Hsync signal is provided
continuously on a dedicated wire. In these systems, the COAST
input and function are unnecessary and should not be used.
In some systems, however, Hsync is disturbed during the
vertical sync period (Vsync). In some cases, Hsync pulses
disappear. In other systems, such as those that employ
composite sync (Csync) signals or embedded sync-on-green,
Hsync can include equalization pulses or other distortions
during Vsync. To avoid upsetting the clock generator during
Vsync, it is important to ignore these distortions. If the pixel
clock PLL sees extraneous pulses, it attempts to lock to this new
frequency, and changes frequency by the end of the Vsync
period. It then takes a few lines of correct Hsync timing to
recover at the beginning of a new frame, resulting in a tearing of
the image at the top of the display.
The COAST input is provided to eliminate this problem. It is an
asynchronous input that disables the PLL input and holds the
clock at its current frequency. The PLL can free run for several
lines without significant frequency drift. Coast can be generated
internally by the AD9984A (see Register 0x18) or can be
provided externally by the graphics controller.
When internal coast is selected (Register 0x18, Bit 7 = 0, and
Register 0x14, Bits[7:6] to select source), Vsync is used as a basis for
determining the position of coast. The internal coast signal is
enabled a programmed number of Hsync periods before the
periodic Vsync signal (Precoast Register 0x16), and it is
dropped a programmed number of Hsync periods after Vsync
(Postcoast Register 0x17). It is recommended that the Vsync
filter be enabled when using the internal coast function to allow
the AD9984A to precisely determine the number of Hsyncs/Vsync
and their location. In many applications where disruptions
occur and coast is used, values of 2 for precoast and 10d for
postcoast are sufficient to avoid most extraneous pulses.
OUTPUT FORMATTER
The output formatter is capable of generating several output
formats to be presented to the 30 data output pins. The output
formats and the pin assignments for each format are listed in
Table 1 2. In addition, there are several clock options for the
output clock. The user can select the pixel clock, a 90° phase-
shifted pixel clock, a 2× pixel clock, or a 0.5× pixel clock for test
purposes. The output clock can also be inverted.
Data output is available as 30-pin RGB or YCbCr, or, if either
4:2:2 or 4:4:4 DDR is selected, a secondary channel is available.
This secondary channel is always 4:2:2 DDR. It contains the
same video data as the primary channel and can be utilized by
either another display or storage device. Depending on the
choice of output modes, the primary output can be 30 pins,
20 pins, or as few as 15 pins.
Mode Descriptions
4:4:4
All channels come out with their 10 data bits at the same time.
Data is aligned to the negative edge of the clock for easy capture.
This is the normal 30-bit output mode for RGB or 4:4:4 YCbCr.
4:2:2
Red and green channels contain 4:2:2 formatted data (20 pins)
with Y data on the green channel and Cb, Cr data on the red
channel. Data is aligned to the negative edge of the clock. The
blue channel contains the secondary channel with Cb, Y, Cr, Y
formatted 4:2:2 DDR data. The data edges are aligned to both
edges of the pixel clock, therefore, using a 90° clock may be
necessary to capture the DDR data.
4:4:4 DDR
This mode puts out full 4:4:4 data on 15 bits of the red and
green channels, thus saving 15 pins. The first half (RGB[14:0])
of the 30-bit data is sent on the rising edge and the second half
(RGB[29:15]) is sent on the falling edge. DDR 4:2:2 data is sent
on the blue channel, as in 4:2:2 mode.
RGB[29:0] = R[9:0] + G[9:0] + B[9:0], so
RGB[29:15] = R[9:0] + G[9:5] and
RGB[14:0] = G[4:0] + B[9:0]
Table 12. Output Formats1
Port Red Green Blue
Bit 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
4:4:4 Red/Cr Green/Y Blue/Cb
4:2:22Cb, Cr Y DDR 4:2:2 ↑Cb,Cr ↓Y, Y
DDR ↑G[4:0] DDR ↑B[9:0] N/A DDR 4:2:2 ↑Cb,Cr
4:4:4
DDR DDR ↓R[9:0] DDR ↓G[9:5] N/A DDR 4:2:2 ↓Y, Y
1 Arrows in table indicate clock edge. Rising edge of clock = ↑, falling edge = ↓.
2 For 4:2:2 modes, Cb is sent before Cr.
AD9984A
Rev. 0 | Page 22 of 44
2-WIRE SERIAL CONTROL PORT
A 2-wire serial control interface is provided with the AD9984A.
Up to two AD9984A devices can be connected to the 2-wire
serial interface with each device having a unique address.
The 2-wire serial interface comprises a clock (SCL) and a bi-
directional data (SDA) pin. The analog flat panel interface acts
as a slave for receiving and transmitting data over the serial
interface. When the serial interface is not active, the logic levels
on SCL and SDA are pulled high by external pull-up resistors.
Data received or transmitted on the SDA line must be stable for
the duration of the positive-going SCL pulse. Data on SDA must
change only when SCL is low. If SDA changes state while SCL is
high, the serial interface interprets that action as a start or stop
sequence.
The following are the five components to serial bus operation:
• Start signal
• Slave address byte
• Base register address byte
• Data byte to read or write
• Stop signal
When the serial interface is inactive (SCL and SDA are high),
communication is initiated by sending a start signal. The start
signal is a high-to-low transition on SDA while SCL is high.
This signal alerts all slaved devices that a data transfer sequence
is coming.
The first 8 bits of data transferred after a start signal comprise a
7-bit slave address (the first seven bits) and a single R/W bit
(the eighth bit). The R/W bit indicates the direction of data
transfer, read from 1 or write to 0 on the slave device. If the
transmitted slave address matches the address of the device, the
AD9984A acknowledges the match by bringing SDA low on the
ninth SCL pulse. If the addresses do not match, the AD9984A
does not acknowledge it.
Table 13. Serial Port Addresses
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1
A6 (MSB) A5 A4 A3 A2 A1 A0
1 0 0 1 1 0 0
1 0 0 1 1 0 1
DATA TRANSFER VIA SERIAL INTERFACE
For each byte of data read or written, the MSB is the first bit in
the sequence.
If the AD9984A does not acknowledge the master device during
a write sequence, the SDA remains high so the master can generate
a stop signal. If the master device does not acknowledge the
AD9984A during a read sequence, the AD9984A interprets this
as end of data. The SDA remains high so the master can generate
a stop signal.
Writing data to specific control registers of the AD9984A
requires writing to the 8-bit address of the control register of
interest after the slave address has been established. This control
register address is the base address for subsequent write operations.
After the initial data byte is written, the base address auto-
increments by one for each additional data byte. If more bytes
are transferred than available addresses, the address does not
increment and remains at its maximum value of 0x44. Any base
address higher than 0x44 does not produce an acknowledge
signal. Data is read from the control registers of the AD9984A in
a similar manner. Reading requires two data transfer operations.
• The base address must be written with the R/W bit of the
slave address byte low to set up a sequential read operation.
Reading (the R/W bit of the slave address byte high) begins
at the previously established base address. The address of the
read register auto-increments after each byte is transferred.
• To terminate a read/write sequence to the AD9984A, a stop
signal must be sent. A stop signal comprises a low-to-high
transition of SDA while SCL is high.
A repeated start signal occurs when the master device driving
the serial interface generates a start signal without first generating
a stop signal to terminate the current communication. This is used
to change the mode of communication (read, write) between
the slave and master without releasing the serial interface lines.
S
D
A
SCL
t
BUFF
t
STAH
t
DHO
t
DSU
t
DAL
t
DAH
t
STASU
t
STOSU
06476-017
Figure 18. Serial Port Read/Write Timing
AD9984A
Rev. 0 | Page 23 of 44
Serial Interface Read/Write Examples
Write to One Control Register
1. Start signal
2. Slave address byte (R/W bit = low)
3. Base address byte
4. Data byte to base address
5. Stop signal
Write To Four Consecutive Control Registers
1. Start signal
2. Slave address byte (R/W bit = low)
3. Base address byte
4. Data byte to base address
5. Data byte to (base address + 1)
6. Data byte to (base address + 2)
7. Data byte to (base address + 3)
8. Stop signal
Read from One Control Register
1. Start signal
2. Slave address byte (R/W bit = low)
3. Base address byte
4. Start signal
5. Slave address byte (R/W bit = high)
6. Data byte from base address
7. Stop signal
Read from Four Consecutive Control Registers
1. Start signal
2. Slave address byte (R/W bit = low)
3. Base address byte
4. Start signal
5. Slave address byte (R/W bit = high)
6. Data byte from base address
7. Data byte from (base address + 1)
8. Data byte from (base address + 2)
9. Data byte from (base address + 3)
10. Stop signal
BIT 7 ACKBIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
SDA
SCL
06476-018
Figure 19. Serial Interface—Typical Byte Transfer
AD9984A
Rev. 0 | Page 24 of 44
2-WIRE SERIAL REGISTER MAP
The AD9984A is initialized and controlled by a set of registers that determine the operating modes. An external controller is employed to
write and read the control registers through the 2-wire serial interface port.
Table 14. Control Register Map
Hex
Address
Read/Write,
Read Only Bits
Default
Value Register Name Description
0x00 RO 7:0 0010 0000 Chip Revision An 8-bit register that represents the silicon revision level.
0x01 R/W7:0 0110 1001 PLL Div MSBs The 8 MSBs (Bits[11:4] of the PLL Divider. Larger values mean the PLL
operates at a faster rate. This register should be loaded first when a
change is needed. (This gives the PLL more time to lock).1
0x02 R/W7:4 1101 **** PLL Div LSBs The 4 LSBs (Bits[3:0]) of the PLL Divider. Links to the PLL Div MSB to
make a 12-bit register.1
0x03 R/W7:6 01** **** VCO/CPMP VCO Range Select. Chooses the VCO frequency range (see the Clock
Generation section).
5:3 **00 1*** Charge Pump Current. Varies the current that drives the low-pass filter
(see the Clock Generation section).
2 **** *0** External Clock Enable.
0x04 R/W7:3 1000 0*** Phase Adjust ADC Clock Phase Adjust. Larger values mean more delay. (1 LSB = T/32).
0x05 R/W6:0 *100 0000 Red Gain MSBs The 7 MSBs of the Red Channel Gain Control. Controls ADC input range
(contrast) of each respective channel. Larger values give less contrast.
0x06 R/W7:6 00** **** Red Gain LSBs The 2 LSBs of the Red Channel Gain Control. Links with Register 0x05
to form the 9-bit red gain that controls the ADC input range (contrast)
of the red channel. A lower value corresponds to a higher gain.1
0x07 R/W6:0 *100 0000 Green Gain MSBs The 7 MSBs of the Green Channel Gain Control. Controls ADC input
range (contrast) of each respective channel. Larger values give less
contrast.
0x08 R/W7:6 00** **** Green Gain LSBs The 2 LSBs of the Green Channel Gain Control. Links to Register 0x07
to form the 9-bit green gain that controls the ADC input range (contrast)
of the green channel. A lower value corresponds to a higher gain.1
0x09 R/W6:0 *100 0000 Blue Gain MSBs The 7 MSBs of the Blue Channel Gain Control. Controls ADC input range
(contrast) of each respective channel. Larger values give less contrast.
0x0A R/W7:6 00** **** Blue Gain LSBs The 2 LSBs of the Blue Channel Gain Control. Links to Register 0x09
to form the 9-bit blue gain that controls the ADC input range (contrast)
of the blue channel. A lower value corresponds to a higher gain.1
0x0B R/W7:0 0100 0000 Red Offset MSBs The 8 MSBs of the Red Channel Offset Control. Controls dc offset
(brightness) of each respective channel. Larger values decrease
brightness.1
0x0C R/W7:5 000* **** Red Offset LSBs The 3 LSBs of the Red Channel Offset Control. Links to Register 0x0B
to form the 11-bit red offset that controls the dc offset (brightness)
of the red channel in auto-offset mode.
0x0D R/W7:0 0100 0000 Green Offset MSBs The 8 MSBs of the Green Channel Offset Control. Controls dc offset
(brightness) of each respective channel. Larger values decrease
brightness.1
0x0E R/W7:5 000* **** Green Offset LSBs The 3 LSBs of the Green Channel Offset Control. Links to Register 0x0D
to form the 11-bit green offset that controls the dc offset (brightness)
of the green channel in auto-offset mode.
0x0F R/W7:0 0100 0000 Blue Offset MSBs The 8 MSBs of the Blue Channel Offset Control. Controls dc offset
(brightness) of each respective channel. Larger values decrease
brightness.1
0x10 R/W7:5 000* **** Blue Offset LSBs The 3 LSBs of the Blue Channel Offset Control. Links to Register 0x0F
to form the 11-bit blue offset that controls the dc offset (brightness)
of the blue channel in auto-offset mode.
0x11 R/W7:0 0010 0000 Sync Separator
Threshold
Sets the threshold of the sync separator’s digital comparator.
0x12 R/W7 0*** **** Hsync Control Hsync Source Override.
0 = The chip determines the active Hsync source.
1 = The active Hsync source is set by Reg. 0x12, Bit 6.
AD9984A
Rev. 0 | Page 25 of 44
Hex
Address
Read/Write,
Read Only Bits
Default
Value Register Name Description
6 *0** **** Hsync Source Select. Determines the source of the Hsync for PLL and
sync processing. This bit is used only if Reg. 0x12, Bit 7 is set to 1 or if
both syncs are active.
0 = Hsync is from HSYNCx input pin.
1 = Hsync is from SOG.
5 **0* **** Hsync Input Polarity Override.
0 = The chip selects the Hsync input polarity.
1 = The input polarity of Hsync is controlled by Reg. 0x12, Bit 4.
4 ***1 **** Hsync Input Polarity. This bit is used only if Reg. 0x12, Bit 5 is set to 1.
0 = Hsync input polarity is negative.
1 = Hsync input polarity is positive.
3 **** 1*** Hsync Output Polarity. Sets the polarity of the Hsync output signal
(HSOUT).
0 = HSOUT polarity is negative.
1 = HSOUT polarity is positive.
0x13 R/W7:0 0010 0000 Hsync Duration Sets the number of pixel clocks that HSOUT is active.
0x14 R/W7 0*** **** Vsync Control Vsync Source Override.
0 = The chip determines the active Vsync source.
1 = The active Vsync source is set by Reg. 0x14, Bit 6.
6 *0** **** Vsync Source Select. Determines the source of Vsync for sync
processing. This bit is used only if Reg. 0x14, Bit 7 is set to 1.
0 = Vsync is from the VSYNCx input pin.
1 = Vsync is from the sync separator.
5 **0* **** Vsync Input Polarity Override.
0 = The chip selects Vsync input polarity.
1 = The input polarity of Vsync is set by Reg. 0x14, Bit 4.
4 ***1 **** Vsync Input Polarity. This bit is used only if Reg. 0x14, Bit 5 is set to 1.
0 = Vsync input polarity is negative.
1 = Vsync input polarity is positive.
3 **** 1*** Vsync Output Polarity. Sets the polarity of the output Vsync signal
(VSOUT).
0 = VSOUT polarity is negative.
1 = VSOUT polarity is positive.
2 **** *0** Vsync Filter Enable. This needs to be enabled when using the Hsync
to Vsync counter.
0 = The Vsync filter is disabled.
1 = The Vsync filter is enabled.
1 **** **0* Vsync Duration Block Enable. This is designed to be used with the
Vsync filter.
0 = Vsync output duration is unchanged.
1 = Vsync output duration is set by Register 0x15.
0x15 R/W7:0 0000 1010 Vsync Duration Sets the number of Hsyncs that Vsync out is active. This is only used if
Reg. 0x14, Bit 1 is set to 1.
0x16 R/W7:0 0000 0000 Precoast The number of Hsync periods to coast prior to Vsync.
0x17 R/W7:0 0000 0000 Postcoast The number of Hsync periods to coast after Vsync.
0x18 R/W7 0*** **** Coast and Clamp
Control
Coast Source. Determines the source of the coast signal.
0 = Using internal coast generated from Vsync.
1 = Using external coast signal from COAST pin.
6 *0** **** Coast Polarity Override.
0 = The chip selects the coast polarity.
1 = The polarity of the coast signal is set by Reg. 0x18, Bit 5.
5 **1* **** Coast Polarity. This bit is used only if Reg. 0x18, Bit 6 is set to 1.
0 = Coast polarity is negative.
1 = Coast polarity is positive.
4 ***0 **** Clamp Source Select. Determines the source of the clamp timing.
0 = Uses the internal clamp generated from Hsync.
1 = Uses the external CLAMP signal.
AD9984A
Rev. 0 | Page 26 of 44
Hex
Address
Read/Write,
Read Only Bits
Default
Value Register Name Description
3 **** 0*** Red Clamp Select.
0 = Clamp the red channel to ground.
1 = Clamp the red channel to midscale.
2 **** *0** Green Clamp Select.
0 = Clamp the green channel to ground.
1 = Clamp the green channel to midscale.
1 **** **0* Blue Clamp Select.
0 = Clamp the blue channel to ground.
1 = Clamp the blue channel to midscale.
0 **** ***0 Must be set to 0 for proper operation.
0x19 R/W7:0 0000 1000 Clamp Placement Places the clamp signal an integer number of clock periods after the
trailing edge of the Hsync signal.
0x1A R/W7:0 0010 0000 Clamp Duration Number of clock periods that the clamp signal is actively clamping.
0x1B R/W7 0*** **** Clamp and Offset Clamp Polarity Override.
0 = The chip selects the clamp polarity.
1 = The polarity of the clamp signal is set by Reg. 0x1B, Bit 6.
6 *1** **** Clamp Polarity. This bit is used only if Reg. 0x1B, Bit 7 is set to 1.
0 = Clamp polarity is negative.
1 = Clamp polarity is positive.
5 **0* **** Auto-Offset Enable.
0 = Auto-offset is disabled.
1 = Auto-offset is enabled (offsets become the desired clamp code).
4:3 ***1 1*** Auto-Offset Update Frequency. This selects how often the auto-
offset circuit operates.
00 = Every 3 clamps.
01 = Every 48 clamps.
10 = Every 192 clamps.
11 = Every 3 Vsync periods.
2:0 **** *011 Must be written to default (011) for proper operation.
0x1C R/W7:0 1111 1111 Test Register 0 Must be set to 0xFF for proper operation.
0x1D R/W7:3 0111 1*** SOG Control SOG Slicer Comparator Threshold. Sets the voltage level of SOG slicer’s
comparator.
2 **** *0** SOGOUT Polarity. Sets the polarity of the signal on the SOGOUT pin.
0 = SOGOUT polarity is negative.
1 = SOGOUT polarity is positive.
1:0 **** **00 SOGOUT Select.
00 = Raw SOGINx.
01 = Raw HSYNCx.
10 = Regenerated Hsync from sync filter.
11 = Filtered Hsync from sync filter.
0x1E R/W7 *** **** Input and Power
Control
Channel Select Override.
0 = The chip determines which input channels to use.
1 = The input channel selection is determined by Reg. 0x1E, Bit 6.
6 *0** **** Channel Select. This is used only if Reg. 0x1E, Bit 7 is set to 1, or if
syncs are present on both channels.
0 = Channel 0 syncs and data are selected.
1 = Channel 1 syncs and data are selected.
5 **1* **** Programmable Bandwidth.
0 = Low analog input bandwidth (~7 MHz).
1 = High analog input bandwidth (~300 MHz).
4 ***1 **** Power-Down Control Select.
0 = Manual power-down control.
1 = Auto power-down control.
3 **** 0*** Power-Down.
0 = Normal operation.
1 = Power-down.
AD9984A
Rev. 0 | Page 27 of 44
Hex
Address
Read/Write,
Read Only Bits
Default
Value Register Name Description
2 **** *0** Power-Down Pin Polarity. Sets the polarity of the signal on the
PWRDN pin.
0 = PWRDN polarity is negative.
1 = PWRDN polarity is positive.
1 **** **0* Power-Down Fast Switching Control.
0 = Normal power-down operation.
1 = The chip stays powered up, and the outputs are put in high
impedance mode.
0 **** ***0 SOGOUT High Impedance Control.
0 = SOGOUT operates as normal during power-down.
1 = SOGOUT is in high impedance during power-down.
0x1F R/W7:5 100* **** Output Select 1 Output Mode.
100 = 4:4:4 RGB mode.
101 = 4:2:2 YCbCr mode.
110 = 4:4:4 DDR mode.
4 ***1 **** Primary Output Enable.
0 = Primary output is in high impedance state.
1 = Primary output is enabled.
3 **** 0*** Secondary Output Enable.
0 = Secondary output is in high impedance state.
1 = Secondary output is enabled.
2:1 **** *10* Output Drive Strength. Applies to all outputs except VSOUT.
00 = Low output drive strength.
01 = Medium output drive strength.
1x = High output drive strength.
0 **** ***0 Output Clock Invert. Applies to all clocks output on DATACK.
0 = Noninverted Pixel Clock.
1 = Inverted Pixel Clock.
0x20 R/W7:6 0*** **** Output Select 2 Output Clock Select.
00 = Pixel clock.
01 = 90° phase-shifted pixel clock.
10 = 2× pixel clock.
11 = 0.5× pixel clock.
5 *0** **** Output High Impedance.
0 = Normal outputs.
1 = All outputs except SOGOUT in high impedance mode.
4 **0* **** SOGOUT High Impedance.
0 = Normal drive.
1 = SOGOUT pin is in high impedance mode.
3 ***0 **** Field Output Polarity. Sets the polarity of the field output signal.
0 = Active low is an even field, active high is an odd field.
1 = Active low is an odd field, active high is an even field.
2 **** 1*** PLL Sync Filter Enable.
0 = PLL uses raw HSYNCx/SOGINx.
1 = PLL uses filtered Hsync/SOG.
1 **** *0** Sync Processing Input Select. Selects the sync source for the sync
processor.
0 = Sync processing uses raw HSYNCx/SOGINx.
1 = Sync processing uses regenerated Hsync from sync filter.
0 **** ***0 Must be set to 1 for proper operation.
0x21 R/W7:0 0010 0000 Must be set to default for proper operation.
0x22 R/W7:0 0011 0010 Must be set to default for proper operation.
0x23 R/W7:0 0000 1010 Sync Filter Window
Width
Sets the window of time around the regenerated Hsync leading
edge (in 25 ns steps) that sync pulses are allowed to pass through.
0x24 RO 7 _*** **** Sync Detect HSYNC0 Detection.
0 = HSYNC0 is not active.
1 = HSYNC0 is active.
AD9984A
Rev. 0 | Page 28 of 44
Hex
Address
Read/Write,
Read Only Bits
Default
Value Register Name Description
6 *_** **** HSYNC1 Detection.
0 = HSYNC1 is not active.
1 = HSYNC1 is active.
5 **_* **** VSYNC0 Detection.
0 = VSYNC0 is not active.
1 = VSYNC0 is active.
4 ***_ **** VSYNC1 Detection.
0 = VSYNC1 is not active.
1 = VSYNC1 is active.
3 **** _*** SOGIN0 Detection.
0 = SOGIN0 is not active.
1 = SOGIN0 is active.
2 **** *_** SOGIN1 Detection.
0 = SOGIN1 is not active.
1 = SOGIN1 is active.
1 **** **_* COAST Detection.
0 = External COAST is not active.
1 = External COAST is active.
0 **** ***_ CLAMP Detection.
0 = External CLAMP is not active.
1 = External CLAMP is active.
0x25 RO 7 _*** **** Sync Polarity Detect
HSYNC0 Polarity.
0 = HSYNC0 polarity is negative.
1 = HSYNC0 polarity is positive.
6 *_** **** HSYNC1 Polarity.
0 = HSYNC1 polarity is negative.
1 = HSYNC1 polarity is active high.
5 **_* **** VSYNC0 Polarity.
0 = VSYNC0 polarity is negative.
1 = VSYNC0 polarity is positive.
4 ***_ **** VSYNC1 Polarity.
0 = VSYNC1 polarity is negative.
1 = VSYNC1 polarity is positive.
3 **** _*** COAST Polarity.
0 = External COAST is negative.
1 = External COAST is positive.
2 **** *_** CLAMP Polarity.
0 = External CLAMP is negative.
1 = External CLAMP polarity is positive.
1 **** **_* Extraneous Pulse Detection.
0 = No extraneous pulses detected on Hsync.
1 = Extraneous pulses detected on Hsync.
0 **** ***_ Sync Filter Lock.
0 = Sync filter unlocked
1 = Sync filter locked.
0x26 RO 7:0 Hsyncs per
Vsync MSBs
MSBs of Hsyncs per Vsync count.
0x27 RO 7:4 Hsyncs per
Vsync LSBs
LSBs of Hsyncs per Vsync count.
0x28 R/W7:0 1011 1111 Test Register 1 Must be written to 0xBF for proper operation.
0x29 R/W7:0 0000 0010 Test Register 2 Must be written to 0x02 for proper operation.
0x2A RO 7:0 Test Register 3 Read only bits for future use.
0x2B RO 7:0 Test Register 4 Read only bits for future use.
0x2C R/W7:5 000* **** Offset Hold Must be written to default for proper operation.
AD9984A
Rev. 0 | Page 29 of 44
Hex
Address
Read/Write,
Read Only Bits
Default
Value Register Name Description
4 ***0 **** Auto-Offset Hold.
Disables the auto-offset and holds the feedback result.
0 = Continuous update.
1 = One time update.
3:0 **** 0000 Must be written to default for proper operation.
0x2D R/W7:0 1111 0000 Test Register 5 Must be written to 0xE8 for proper operation.
0x2E R/W7:0 1111 0000 Test Register 6 Must be written to 0xE0 for proper operation.
0x34 R/W2 **** *0** SOG Filter SOG Filter Enable. When enabled, filters out SOG inputs less than 250 ns.
0 = SOG filter disabled.
1 = SOG filter enabled.
0x36 R/W0 **** ***0 VCO Gear VCO Gear Select. Adds another range to the VCO. Used for lower
frequencies only.
0 = Disable low VCO gear.
1 = Enable low VCO gear.
0x3C R/W7:4 0000 **** Auto Gain Test Bits. Must be set to default for proper operation.
3 **** 0*** Auto Gain Matching Hold.
0 = Disables auto gain updates and holds the current auto offset values.
1 = Allows auto gain to continuously update.
2:0 **** *000 Auto Gain Matching Enable.
000 = Auto gain matching is disabled.
110= Auto gain matching is enabled.
1 Functions with more than eight control bits, such as PLL divide ratio, gain, and offset, are only updated when the LSBs are written to (for example, Register 0x02 for
PLL divide ratio).
AD9984A
Rev. 0 | Page 30 of 44
2-WIRE SERIAL CONTROL REGISTERS
CHIP IDENTIFICATION
0x00—Bits[7:0] Chip Revision
This is an 8-bit register that represents the silicon revision.
PLL DIVIDER CONTROL
0x01—Bits[7:0] PLL Divide Ratio MSBs
These are the 8 MSBs of the 12-bit PLL divide ratio (PLLDIV).
The PLL derives a pixel clock from the incoming Hsync signal.
The pixel clock frequency is then divided by an integer value,
such that the output is phase-locked to Hsync. This PLLDIV
value determines the number of pixel times (pixels plus
horizontal blanking overhead) per line. This is typically 20% to
30% more than the number of active pixels in the display.
The 12-bit value of the PLL divider supports divide ratios from
2 to 4095 as long as the output frequency is within range. The
higher the value loaded in this register, the higher the resulting
clock frequency with respect to a fixed Hsync frequency.
VESA has established some standard timing specifications that
assist in determining the value for PLLDIV as a function of
horizontal and vertical display resolution and frame rate (see
Table 1 0). However, many computer systems do not precisely
conform to the recommendations. As a result, these numbers
should be used only as a guide. The display system manufac-
turer should provide automatic or manual means for optimizing
PLLDIV. An incorrectly set PLLDIV usually produces one or
more vertical noise bars on the display. The greater the error,
the greater the number of bars produced.
The power-up default value of PLLDIV is 1693.
PLLDIVM = 0x69, PLLDIVL = 0xDX.
The AD9984A updates the full divide ratio only when the LSBs are
written. Writing to this register by itself does not trigger an update.
0x02—Bits[7:4] PLL Divide Ratio LSBs
These are the four LSBs of the 12-bit PLL divide ratio (PLLDIV).
The power-up default value of PLLDIV is 1693. PLLDIVM = 0x69,
PLLDIVL = 0xDX.
CLOCK GENERATOR CONTROL
0x03—Bits[7:6] VCO Range Select
These two bits establish the operating range of the clock
generator. VCO range must be set to correspond to the desired
operating frequency (incoming pixel rate). The PLL gives the
best jitter performance at high frequencies. For this reason, to
output low pixel rates and still achieve good jitter performance,
the PLL operates at a higher frequency, but then divides down
the clock rate afterwards. See Table 15 for the pixel rates of each
VCO range setting. The PLL output divisor is automatically
selected with the VCO range setting. The power-up default
value is 01.
Table 15. VCO Range Select Bits
Value Result (Pixel Rates)
00 10 to 31
01 31 to 62
10 62 to 124
11 124 to 170
0x03—Bits[5:3] Charge Pump Current
These three bits establish the current driving the loop filter in
the clock generator. The current must be set to correspond with
the desired operating frequency. The power-up default value is
current = 001.
Table 16. Charge Pump Current Bits
Ip2 Ip1 Ip0 Result (Current)
0 0 0 50
0 0 1 100
0 1 0 150
0 1 1 250
1 0 0 350
1 0 1 500
1 1 0 750
1 1 1 1500
0x03—Bit[2] External Clock Enable
This bit determines the source of the pixel clock.
Table 17. External Clock Enable Bit
Value Result
0 Internally generated clock.
1 Externally provided clock signal.
A Logic 0 enables the internal PLL that generates the pixel clock
from an externally provided Hsync.
A Logic 1 enables the external EXTCK input pin. In this mode,
the PLL divide ratio (PLLDIV) is ignored. The clock phase
adjust (Phase) is still functional. The power-up default value is
EXTCK = 0.
PHASE ADJUST
0x04—Bits[7:3] ADC Clock Phase Adjust
These bits adjust the phase for the DLL to generate the ADC
clock. The 5-bit value adjusts the sampling phase in 32 steps
across one pixel time. Each step represents an 11.25° shift in
sampling phase. The power-up default is 16.
INPUT GAIN
The AD9984A can accommodate input signals with a full-scale
range between 0.5 V and 1.0 V p-p. Setting the red, green, or
blue channel gain to 511 corresponds to an input range of 1.0 V.
A red, green, or blue channel gain of 0 establishes an input range of
0.5 V. Note that increasing gain results in the picture having less
contrast (the input signal uses fewer available converter codes).
AD9984A
Rev. 0 | Page 31 of 44
0x05—Bits[6:0] Red Channel Gain Control MSBs
This register contains the 7-bit MSBs of the red channel gain
control. Values written to this register are not updated until the
LSB register (Register 0x06) has also been written to. The
power-up default is 1000000.
0x06 —Bits[7:6] Red Channel Gain Control LSBs
This register contains the 2-bit LSBs of the red channel gain
control. Along with the 7 MSBs of gain control in Register 0x05,
there are 9 bits of gain control. Default power-up value is 00.
0x07—Bits[6:0] Green Channel Gain Control MSBs
This register contains the 7-bit MSBs of the green channel gain
control. Register update requires writing 0x00 to Register 0x08.
0x08—Bits[7:6] Green Channel Gain Control LSBs
This register contains the 2-bit LSBs of the green channel gain
control. Along with the 7 MSBs of gain control in Register 0x07,
there are 9 bits of gain control. Default power-up value is 00.
0x09—Bits[6:0] Blue Channel Gain Control MSBs
This register contains the 7-bit MSBs of the blue channel gain
control. Register update requires writing 0x00 to Register 0x0A.
0x0A—Bits[7:6] Blue Channel Gain Control LSBs
This register contains the 2-bit LSBs of the blue channel gain
control. Along with the 7 MSBs of gain control in Register 0x09,
there are 9 bits of gain control. Default power-up value is 00.
INPUT OFFSET
The offset control shifts the analog input, resulting in a change
in brightness. Note that the function of the red, blue, or green
channel offset registers depends on whether auto-offset is
enabled (Register 0x1B, Bit 5).
If auto-offset is disabled, nine bits of the offset registers
(Bits[6:0] of the offset MSB register plus Bits[7:6] of the following
register) control the absolute offset added to the channel (for
the red channel, Register 0x0B, Bits[6:0] plus Register 0x0C,
Bits[7:6]) control the absolute offset added to the channel. The
offset control provides a ±255 LSBs of adjustment range, with
1 LSB of offset corresponding to 1 LSB of output code.
If auto-offset is enabled, the 11-bit offset (comprised of the
8 bits of the MSB register and Bits[7:5] of the following LSB
register) determines the clamp target code. The 11-bit offset
consists of 1 sign bit plus 10 bits. If the register is programmed to
530d, the output code is equal to 530d at the end of the clamp
period. Note that incrementing the offset register setting by
1 LSB adds 1 LSB of offset, regardless of the auto-offset setting.
0x0B—Bits[7:0] Red Channel Offset Control MSBs
This register is the 8-bit MSBs of the red channel offset control.
Along with the 3 LSBs in the red channel offset in Register 0x0C,
there are 11 bits of dc offset control in the red channel. Values
written to this register are not updated until the LSB register
(Register 0x0C) has also been written to.
0x0C—Bits[7:5] Red Channel Offset Control LSBs
This register contains the 3-bit LSBs of the red channel offset
control. Combining these bits with the 8 bits of MSBs in
Register 0x0B creates 11 bits of offset control.
0x0D—Bits[7:0] Green Channel Offset Control MSBs
This register contains the 8-bit MSBs of the green channel offset
control. Update of this register occurs only when Register 0x0E
is also written to.
0x0E—Bits[7:5] Green Channel Offset Control LSBs
This register contains the 3-bit LSBs of the green channel offset
control. Combining these bits with the 8 bits of MSBs in the
Register 0x0D makes 11 bits of offset control.
0x0F—Bits[7:0] Blue Channel Offset Control MSBs
The 8-bit blue channel offset control. Update of this register
occurs only when Register 0x10 is also written to.
0x10—Bits[7:5] Blue Channel Offset Control LSBs
The LSBs of the blue channel offset control combine with the
8 bits of MSBs in the Register 0x0F to make 11 bits of offset control.
HSYNC CONTROL
0x11—Bits[7:0] Sync Separator Threshold
This register sets the threshold of the sync separator’s digital
comparator. The value written to this register is multiplied by
200 ns to get the threshold value. Therefore, if a value of 5 is
written, the digital comparator threshold is 1 μs and any pulses
less than 1 μs are rejected by the sync separator. There is some
variability to the 200 ns multiplier value. The maximum
variability over all operating conditions is ±20% (160 ns to
240 ns). Because normal Vsync and Hsync pulse widths differ
by a factor of about 500 or more, the 20% variability is not an
issue. The power-up default value is 32d.
0x12—Bit[7] Hsync Source Override
This bit is the Hsync source override. Setting this bit to 0 allows
the chip to determine the active Hsync source. Setting it to 1
uses Bit 6 of Register 0x12 to determine the active Hsync
source. Power-up default value is 0.
Table 18. Hsync Source Override Bit
Value Result
0 Hsync source determined by chip.
1 Hsync source determined by user (Register 0x12, Bit 6).
0x12—Bit[6] Hsync Source Select
This bit selects the source of the Hsync for PLL and sync processing
(only if Bit 7 of Register 0x12 is set to 1 or if both syncs are active).
Setting this bit to 0 specifies the Hsync from the input pin.
Setting it to 1 selects Hsync from SOG. Power-up default is 0.
Table 19. Hsync Source Select Bit
Value Result
0 HSYNCx input.
1 Hsync from SOG.
AD9984A
Rev. 0 | Page 32 of 44
0x12—Bit[5] Hsync Input Polarity Override
This bit determines whether the chip selects the Hsync input
polarity or if it is specified. Setting this bit to 0 allows the chip
to automatically select the polarity of the input Hsync. Setting it
to 1 indicates that Bit 4 of Register 0x12 specifies the polarity.
Power-up default is 0.
Table 20. Hsync Input Polarity Override Bit
Value Result
0 Hsync polarity determined by chip.
1 Hsync polarity determined by user (Register 0x12, Bit 4).
0x12—Bit[4] Hsync Input Polarity
If Bit 5 of Register 0x12 is 1, the value of this bit specifies the
polarity of the input Hsync. Setting this bit to 0 indicates a
negative Hsync input polarity. Setting this bit to 1 indicates a
positive Hsync input polarity. Power-up default is 1.
Table 21. Hsync Input Polarity Bit
Value Result
0 Hsync input polarity is negative.
1 Hsync input polarity is positive.
0x12—Bit[3] Hsync Output Polarity
This bit sets the polarity of the Hsync output (HSOUT). Setting
this bit to 0 indicates a negative HSOUT polarity. Setting this bit
to 1 indicates a positive HSOUT polarity.
Table 22. Hsync Output Polarity Bit
Value Result
0 HSOUT polarity is negative.
1 HSOUT polarity is positive.
0x13—Bits[7:0] Hsync Duration
This 8-bit register sets the duration of the HSOUT pulse. The
leading edge of the Hsync output is triggered by the internally
generated, phase-adjusted, PLL feedback clock. The AD9984A
then counts a number of pixel clocks equal to the value in this
register. This triggers the trailing edge of HSOUT, which is also
phase-adjusted.
VSYNC CONTROL
0x14—Bit[7] Vsync Source Override
This bit is the active Vsync override. Setting this to 0 allows the
chip to determine the active Vsync source, setting it to 1 uses
Bit 6 of Register 0x14 to determine the active Vsync source.
Power-up default value is 0.
Table 23. Vsync Source Override Bit
Value Result
0 Vsync source determined by chip.
1 Vsync source determined by user (Register 0x14, Bit 6).
0x14—Bit[6] Vsync Source Select
This bit selects the source of the Vsync for sync processing only
if Bit 7 of Register 0x14 is set to 1. Setting Bit 6 to 0 specifies the
Vsync from the input pin. Setting it to 1 selects Vsync from the
sync separator. Power-up default is 0.
Table 24. Vsync Source Select Bit
Value Result
0 Vsync from VSYNCx input pin.
1 Vsync from sync separator.
0x14—Bit[5] Vsync Input Polarity Override
This bit sets whether the chip selects the Vsync input polarity or
if it is specified. Setting this bit to 0 allows the chip to
automatically select the polarity of the input Vsync. Setting this
bit to 1 indicates that Bit 4 of Register 0x14 specifies the
polarity. Power-up default is 0.
Table 25. Vsync Input Polarity Override Bit
Value Result
0 Vsync polarity determined by chip.
1 Vsync polarity determined by user (Register 0x14, Bit 4).
0x14—Bit[4] Vsync Input Polarity
If Bit 5 of Register 0x14 is 1, the value of this bit specifies the
polarity of the input Vsync. Setting this bit to 0 indicates a
negative Vsync input polarity. Setting this bit to 1 indicates a
positive Vsync input polarity. Power-up default is 1.
Table 26. Vsync Input Polarity Bit
Value Result
0 Vsync input polarity is negative.
1 Vsync input polarity is positive.
0x14—Bit[3] Vsync Output Polarity
This bit sets the polarity of the Vsync output (VSOUT). Setting
this bit to 0 indicates a negative VSOUT polarity. Setting this bit
to 1 indicates a positive VSOUT polarity. Power-up default is 1.
Table 27. Vsync Output Polarity Bit
Value Result
0 VSOUT polarity is negative.
1 VSOUT polarity is positive.
0x14—Bit[2] Vsync Filter Enable
This bit enables the Vsync filter allowing precise placement of
the Vsync with respect to the Hsync and facilitating the correct
operation of the Hsyncs/Vsync count.
Table 28. Vsync Filter Enable Bit
Value Result
0 Vsync filter disabled.
1 Vsync filter enabled.
AD9984A
Rev. 0 | Page 33 of 44
0x14—Bit[1] Vsync Duration Block Enable
This enables the Vsync duration block, which is designed to be
used with the Vsync filter. Setting the bit to 0 leaves the Vsync
output duration unchanged. Setting the bit to 1 sets the Vsync
output duration based on Register 0x15. Power-up duration is 0.
Table 29. Vsync Duration Block Enable Bit
Value Result
0 Vsync output duration is unchanged.
1 Vsync output duration is set by Register 0x15.
0x15—Bits[7:0] Vsync Duration
This register is used to set the output duration of the Vsync, and
is designed to be used with the Vsync filter. This is valid only if
Register 0x14, Bit 1 is set to 1. Power-up default is 10d.
COAST AND CLAMP CONTROLS
0x16—Bits[7:0] Precoast
This register allows the internally generated coast signal to be
applied prior to the Vsync signal. This is necessary in cases
where pre-equalization pulses are present. The step size for this
control is one Hsync period. For precoast to work correctly, it is
necessary for both the Vsync filter (Register 0x14, Bit 2) and
sync processing filter (Register 0x20, Bit 1) to either be enabled
or disabled. The power-up default is 00.
0x17—Bits[7:0] Postcoast
This register allows the internally generated coast signal to be
applied following the Vsync signal. This is necessary in cases
where post equalization pulses are present. The step size for this
control is one Hsync period. For postcoast to work correctly, it
is necessary for both the Vsync filter (Register 0x14, Bit 2) and
sync processing filter (Register 0x20, Bit 1) to be enabled or
disabled. The power-up default is 00.
0x18—Bit[7] Coast Source
This bit is used to select the active coast source. The choices are
the COAST input pin or Vsync. If Vsync is selected, the addi-
tional decision of using the VSYNCx input pin or the output from
the sync separator needs to be made (Register 0x14, Bits[7:6]).
Table 30. Coast Source Bit
Value Result
0 Vsync (internal coast).
1 COAST pin.
0x18—Bit[6] Coast Polarity Override
This register is used to override the internal circuitry that
determines the polarity of the coast signal going into the PLL.
The power-up default setting is 0.
Table 31. Coast Polarity Override Bit
Value Result
0 Coast polarity determined by chip.
1 Coast polarity determined by user (Register 0x18, Bit 5).
0x18—Bit[5] Input Coast Polarity
This register sets the input coast polarity when Bit 6 of Register
0x18 is 1. The power-up default setting is 1.
Table 32. Input Coast Polarity Bit
Value Result
0 Coast polarity is negative.
1 Coast polarity is positive.
0x18—Bit[4] Clamp Source Select
This bit determines the source of clamp timing. A 0 enables the
clamp timing circuitry controlled by clamp placement and
clamp duration. The clamp position and duration is counted
from the leading edge of Hsync. A 1 enables the external
CLAMP input pin. The three channels are clamped when the
clamp signal is active. The polarity of clamp is determined by
the CLAMP polarity bit. The power-up default setting is 0.
Table 33. Clamp Source Select Bit
Value Result
0 Internally generated clamp.
1 Externally provided clamp signal (CLAMP).
0x18—Bit[3] Red Clamp Select
This bit determines whether the red channel is clamped to
ground or to midscale. The power-up default setting is 0.
Table 34. Red Clamp Select Bit
Value Result
0 Clamp to ground.
1 Clamp to midscale.
0x18—Bit[2] Green Clamp Select
This bit determines whether the green channel is clamped to
ground or to midscale. The power-up default setting is 0.
Table 35. Green Clamp Select Bit
Value Result
0 Clamp to ground.
1 Clamp to midscale.
0x18—Bit[1] Blue Clamp Select
This bit determines whether the blue channel is clamped to
ground or to midscale. The power-up default setting is 0.
Table 36. Blue Clamp Select Bit
Value Result
0 Clamp to ground.
1 Clamp to midscale.
0x18—Bit[0]
Must be set to 0 for proper operation.
AD9984A
Rev. 0 | Page 34 of 44
0x19—Bits[7:0] Clamp Placement
An 8-bit register that sets the position of the internally generated
clamp. When clamp source select = 0 (Register 0x18, Bit 4), a
clamp signal is generated internally at a position established by
this register and for a duration set by the clamp duration register
(Register 0x1A). Clamping is started at the clamp placement
count of pixel periods after the trailing edge of Hsync. The clamp
placement can be programmed to any value between 1 and 255.
A value of 0 is not supported.
The clamp should be placed during a time that the input signal
presents a stable black-level reference, usually the back porch
period between Hsync and the image. When clamp source = 1,
this register is ignored. Power-up default setting is 8.
0x1A—Bits[7:0] Clamp Duration
An 8-bit register that sets the duration of the internally generated
clamp. When the clamp source select is 0 (Register 0x18, Bit 4),
a clamp signal is generated internally at a position established
by the clamp placement register (Register 0x19) for a duration
set by this clamp duration register. Clamping begins a clamp
placement count (Register 0x19) of pixel periods after the trailing
edge of Hsync. The clamp duration can be programmed to any
value between 1 and 255. A value of 0 is not supported.
For the best results, the clamp duration should be set to include
the majority of the black reference signal time that follows the
Hsync signal trailing edge. Insufficient clamping time can
produce brightness changes at the top of the screen, and a slow
recovery from large changes in the average picture level (APL)
or brightness. When EXTCLMP = 1, this register is ignored.
Power-up default setting is 20d.
0x1B—Bit[7] Clamp Polarity Override
This bit is used to override the internal circuitry that
determines the polarity of the clamp signal. The power-up
default setting is 0.
Table 37. Clamp Polarity Override Bit
Value Result
0 Clamp polarity determined by chip.
1 Clamp polarity determined by user (Register 0x1B, Bit 6).
0x1B—Bit[6] Clamp Polarity
This bit indicates the polarity of the clamp signal only if Bit 7 of
Register 0x1B = 1. The power-up default setting is 1.
Table 38. Clamp Polarity Bit
Value Result
0 Clamp polarity is negative.
1 Clamp polarity is positive.
0x1B—Bit[5] Auto-Offset Enable
This bit selects between auto-offset mode and manual offset
mode (auto-offset disabled). See the Automatic Offset section
for more information. The power-up default setting is 0.
Table 39. Auto-Offset Enable Bit
Value Result
0 Auto-offset is disabled.
1 Auto-offset is enabled (manual offset mode).
0x1B—Bits[4:3] Auto-Offset Update Frequency
These bits control how often the auto-offset circuit is updated
(if enabled). Updating every 192 Hsyncs recommended. The
power-up default setting is 11.
Table 40. Auto-Offset Update Frequency Bits
Value Result
00 Update offset every 3-clamp periods.
01 Update offset every 48-clamp periods.
10 Update offset every 192-clamp periods.
11 Update offset every 3 Vsync periods.
0x1B—Bits[2:0]
Must be written to 011 for proper operation.
0x1C—Bits[7:0] Test Register 0
Must be set to 0xFF for proper operation.
SOG CONTROL
0x1D—Bits[7:3] SOG Slicer Comparator Threshold
These register bits adjust the comparator threshold of the SOG
slicer in steps of 8 mV, with the minimum setting equaling
8 mV and the maximum setting equaling 256 mV. The power-
up default setting is 15d and corresponds to a threshold value of
128 mV.
0x1D—Bit[2] SOGOUT Polarity
This bit sets the polarity of the SOGOUT signal. The power-up
default setting is 0.
Table 41. SOGOUT Polarity Bit
Value Result
0 SOGOUT polarity is negative.
1 SOGOUT polarity is positive.
0x1D—Bits[1:0] SOGOUT Select
These register bits control what is output on the SOGOUT pin.
Options are the raw SOGINx from the slicer (that is, the unproc-
essed SOG signal produced from the sync slicer), the raw HSYNCx,
the regenerated Hsync from the sync filter that can generate
missing syncs due to coasting or drop-out, or finally, the filtered
Hsync that excludes extraneous syncs that do not occur within
the sync filter window. The power-up default setting is 0.
Table 42. SOGOUT Select Bits
Value Result
00 Raw SOGINx.
01 Raw HSYNCx.
10 Regenerated Hsync from sync filter.
11 Filtered Hsync from sync filter.
AD9984A
Rev. 0 | Page 35 of 44
INPUT AND POWER CONTROL
0x1E—Bit[7] Channel Select Override
This bit provides an override to the automatic input channel
selection. Power-up default setting is 0.
Table 43. Channel Select Override Bit
Value Result
0 Channel input source determined by chip.
1 Channel input source determined by user,
(Register 0x1E, Bit 6).
0x1E—Bit[6] Channel Select
This bit selects the active input channel if Bit 7 of Register 0x1E
is 1. This selects between Channel 0 data and syncs or Channel 1
data and syncs. Power-up default setting is 0.
Table 44. Channel Select Bit
Value Result
0 Channel 0 data and syncs are selected.
1 Channel 1 data and syncs are selected.
0x1E—Bit[5] Programmable Bandwidth
This bit selects between a low or high input bandwidth; having
a low input bandwidth is useful in limiting noise for lower
frequency inputs. The power-up default setting is 1. Low analog
input bandwidth is ~7 MHz; high analog input bandwidth is
~300 MHz.
Table 45. Programmable Bandwidth Bit
Value Result
0 Low analog input bandwidth.
1 High analog input bandwidth.
0x1E—Bit[4] Power-Down Control Select
This bit determines whether power-down is controlled manually or
automatically by the chip. If automatic control is selected (by
setting this bit to 1), the AD9984A’s decision is based on the
status of the some of the sync detect bits (Register 0x24, Bit 2,
Bit 3, Bit 6, and Bit 7). If either an Hsync or a sync-on-green
input is detected on any input, the chip powers up or powers
down. For manual control, the AD9984A allows the flexibility
of control through both a dedicated pin and a register bit. The
dedicated pin allows a hardware watchdog circuit to control
power-down, whereas the register bit allows power-down to be
controlled by software. With manual power-down control, the
polarity of the power-down pin must be set (Register 0x1E, Bit 2)
whether it is used or not. If unused, it is recommended to set
the polarity to active high and hardwire the pin to ground with a
10 kΩ resistor.
Table 46. Power-Down Control Select Bit
Value Result
0 Manual power-down control (user determines
power-down).
1 Auto power-down control (chip determines
power-down).
0x1E—Bit[3] Power-Down
This bit is used to manually place the chip in power-down
mode. It is only used if manual power-down control is selected
(Register 0x1E, Bit 4 = 0). Both the state of this register bit
and the power-down pin (Pin 17) are used to control manual
power-down. (See the Power Management section for more
details on power-down.)
Table 47. Power-Down Bit
Value Pin 17 Result
0 0 Normal operation.
1 X Power-down.
0x1E—Bit[2] Power-Down Pin Polarity
This bit defines the polarity of the power-down pin (Pin 17).
It is only used if manual power-down control is selected
(Register 0x1E, Bit 4 = 0).
Table 48. Power-Down Pin Polarity Bit
Value Result
0 PWRDN polarity is negative.
1 PWRDN polarity is positive.
0x1E—Bit[1] Power-Down Fast Switching Control
This bit controls a special fast switching mode. With this bit, the
AD9984A can stay active during power-down and only puts the
outputs in high impedance. This option is useful when the data
outputs from two chips are connected on a PCB and the user
wants to instantaneously switch between the two.
Table 49. Power-Down Fast Switching Control Bit
Value Result
0 Normal power-down operation.
1 The chip stays powered up, and the outputs are put
in high impedance mode.
0x1E—Bit[0] SOGOUT High Impedance Control
This bit controls whether or not the SOGOUT output pin is in
high impedance when in power-down mode. In most cases,
SOGOUT is not put in high impedance during normal operation
because it is usually needed for sync detection by the graphics
controller. The option to put SOGOUT in high impedance is
included mainly to allow for factory testing modes.
Table 50. SOGOUT High Impedance Control Bit
Value Result
0 The SOGOUT operates as normal during power-down.
1 The SOGOUT is in high impedance during
power-down.
OUTPUT CONTROL
0x1F—Bits[7:5] Output Mode
These bits choose between three options for the output mode.
In 4:4:4 mode, RGB is standard. In 4:2:2 mode, YCbCr is standard,
which reduces the number of output pins from 30 to 20. In 4:4:4
DDR output mode, the data is in RGB mode, but changes on
every clock edge. The power-up default setting is 100.
AD9984A
Rev. 0 | Page 36 of 44
Table 51. Output Mode Bits
Value Result
100 4:4:4 RGB mode.
101 4:2:2 YCbCr mode.
110 4:4:4 DDR mode.
0x1F—Bit[4] Primary Output Enable
This bit places the primary output in active or high impedance
mode. The power-up default setting is 1.
Table 52. Primary Output Enable Bit
Value Result
0 Primary output is in high impedance mode.
1 Primary output is enabled.
0x1F—Bit[3] Secondary Output Enable
This bit places the secondary output in active or high
impedance mode.
The secondary output is designated when using either 4:2:2 or
4:4:4 DDR. In these modes, the data on the blue output channel
is the secondary output while the output data on the red and
green channels are the primary output. Secondary output is
always a DDR YCbCr data mode. See the Output Formatter
section and Table 12. The power-up default setting is 0.
Table 53. Secondary Output Enable Bit
Value Result
0 Secondary output is in high impedance mode.
1 Secondary output is enabled.
0x1F—Bits[2:1] Output Drive Strength
These two bits select the drive strength for all the high speed
digital outputs (except VSOUT, A0, and O/E FIELD). Higher
drive strength results in faster rise/fall times and, in general,
makes it easier to capture data. Lower drive strength results in
slower rise/fall times and helps to reduce EMI and digitally gen-
erated power supply noise. The power-up default setting is 10.
Table 54. Output Drive Strength Bits
Value Result
00 Low output drive strength.
01 Medium output drive strength.
1x High output drive strength.
0x1F—Bit[0] Output Clock Invert
This bit allows inversion of the output clock. The power-up
default setting is 0.
Table 55. Output Clock Invert Bit
Value Result
0 Noninverted pixel clock.
1 Inverted pixel clock.
0x20—Bits[7:6] Output Clock Select
These bits selects the optional output clocks such as a fixed 40 MHz
internal clock, a 2× clock, a 90° phase-shifted clock, or the normal
pixel clock. The power-up default setting is 00.
Table 56. Output Clock Select Bits
Value Result
00 Pixel clock.
01 90° phase-shifted pixel clock.
10 2× pixel clock.
11 0.5× pixel clock.
0x20—Bit[5] Output High Impedance
This bit puts all outputs (except SOGOUT) in a high impedance
state. The power-up default setting is 0.
Table 57. Output High Impedance Bit
Value Result
0 Normal outputs.
1 All outputs (except SOGOUT) in high impedance mode.
0x20—Bit[4] SOGOUT High Impedance
This bit allows the SOGOUT pin to be placed in high
impedance mode. The power-up default setting is 0.
Table 58. SOGOUT High Impedance Bit
Value Result
0 Normal drive.
1 SOGOUT pin is in high impedance mode.
0x20—Bit[3] Field Output Polarity
This bit sets the polarity of the field output bit. The power-up
default setting is 1.
Table 59. Field Output Polarity Bit
Value Result
0 Active low = even field, active high = odd field.
1 Active low = odd field, active high = even field.
SYNC PROCESSING
0x20—Bit[2] PLL Sync Filter Enable
This bit selects which signal the PLL uses. It can select between
raw versions of HSYNCx/SOGINx and filtered versions of
Hsync/SOG. The filtering of the Hsync and SOG can eliminate
nearly all extraneous transitions that have traditionally caused
PLL disruption. The power-up default setting is 0.
Table 60. PLL Sync Filter Enable Bit
Value Result
0 PLL uses raw HSYNCx or SOGINx.
1 PLL uses filtered Hsync or SOG.
0x20—Bit[1] Sync Processing Input Select
This bit selects whether the sync processor uses a raw sync or a
regenerated Hsync for the following functions: coast, Hsyncs
per Vsync count, field detection, and Vsync duration counts.
Using the regenerated Hsync is recommended.
Table 61. Sync Processing Input Select Bit
Value Result
0 Sync processing uses raw HSYNCx or SOGINx.
1 Sync processing uses the internally regenerated
Hsync.
AD9984A
Rev. 0 | Page 37 of 44
0x20—Bit[0]
Must be set to 1 for proper operation.
0x21—Bits[7:0]
Must be set to default.
0x22—Bits[7:0]
Must be set to default.
0x23—Bits[7:0] Sync Filter Window Width
This 8-bit register sets the window of time for the regenerated
Hsync leading edge (in 25 ns steps) and the time that sync
pulses are allowed to pass through. Therefore, with the
default value of 10, the window width is ±250 ns. The goal is
to set the window width to reject extraneous pulses (see the
Sync Processing section). As with the sync separator threshold,
the 25 ns multiplier value is somewhat variable. The maximum
variability over all operating conditions is ±20% (20 ns to 30 ns).
DETECTION STATUS
0x24—Bit[7] HSYNC0 Detection
This bit is used to indicate when activity is detected on the
HSYNC0 input pin. If HSYNC0 is held high or low, activity is
not detected. The sync processing block diagram (Figure 9)
shows where this function is implemented.
Table 62. HSYNC0 Detection Bit
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[6] HSYNC1 Detection
This bit is used to indicate when activity is detected on the
HSYNC1 input pin. If HSYNC1 is held high or low, activity is
not detected. Figure 9 shows where this function is implemented.
Table 63. HSYNC1 Detection Results
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[5] VSYNC0 Detection
This bit is used to indicate when activity is detected on the
VSYNC0 input pin. If VSYNC0 is held high or low, activity is
not detected. Figure 9 shows where this function is implemented.
Table 64. VSYNC0 Detection Results
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[4] VSYNC1 Detection
This bit is used to indicate when activity is detected on the
VSYNC1 input pin. If VSYNC1 is held high or low, activity is
not detected. Figure 9 shows where this function is implemented.
Table 65. VSYNC1 Detection Bit
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[3] SOGIN0 Detection
This bit is used to indicate when activity is detected on the
SOGIN0 pin. If SOGIN0 is held high or low, activity is not
detected. Figure 9 shows where this function is implemented.
Table 66. SOGIN0 Detection Bit
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[2] SOGIN1 Detection
This bit is used to indicate when activity is detected on the
SOGIN1 input pin. If SOGIN1 is held high or low, activity is not
detected. Figure 9 shows where this function is implemented.
Table 67. SOGIN1 Detection Bit
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[1] COAST Detection
This bit detects activity on the EXTCK/COAST pin. It indicates
that one of the two signals is active, but it does not indicate
which one. A dc signal is not detected.
Table 68. COAST Detection Bit
Value Result
0 No activity detected.
1 Activity detected.
0x24—Bit[0] CLAMP Detection
This bit is used to indicate when activity is detected on the
external CLAMP pin. If external CLAMP is held high or low,
activity is not detected.
Table 69. CLAMP Detection Bit
Value Result
0 No activity detected.
1 Activity detected.
POLARITY STATUS
0x25—Bit[7] HSYNC0 Polarity
This bit indicates the polarity of HSYNC0 input.
Table 70. HSYNC0 Polarity Bit
Value Result
0 HSYNC0 polarity is negative.
1 HSYNC0 polarity is positive.
AD9984A
Rev. 0 | Page 38 of 44
0x25—Bit[6] HSYNC1 Polarity
This bit indicates the polarity of HSYNC1 input.
Table 71. HSYNC1 Polarity Bit
Value Result
0 HSYNC1 polarity is negative.
1 HSYNC1 polarity is positive.
0x25—Bit[5] VSYNC0 Polarity
This bit indicates the polarity of VSYNC0 input.
Table 72. VSYNC0 Polarity Bit
Value Result
0 VSYNC0 polarity is negative.
1 VSYNC0 polarity is positive.
0x25—Bit[4] VSYNC1 Polarity
This bit indicates the polarity of VSYNC1 input.
Table 73. VSYNC1 Polarity Bit
Value Result
0 VSYNC1 polarity is negative.
1 VSYNC1 polarity is positive.
0x25—Bit[3] COAST Polarity
This bit indicates the polarity of the external COAST signal.
Table 74. COAST Polarity Bit
Value Result
0 COAST polarity is negative.
1 COAST polarity is positive.
0x25—Bit[2] CLAMP Polarity
This bit indicates the polarity of the CLAMP signal.
Table 75. CLAMP Polarity Bit
Value Result
0 CLAMP polarity is negative.
1 CLAMP polarity is positive.
0x25—Bit[1] Extraneous Pulse Detection
A second output from the Hsync filter, this status bit tells
whether extraneous pulses are present on the incoming sync
signal. Often, extraneous pulses are used for copy protection, so
this status bit can be used for this purpose.
Table 76. Extraneous Pulse Detection Bit
Value Result
0 No extraneous pulses detected during active Hsync.
1 Extraneous pulses detected during active Hsync.
0x25—Bit[0] Sync Filter Lock
When this bit is set to 1, the sync filter is locked. When set to 0,
the sync filer is unlocked.
HSYNC COUNT
0x26—Bits[7:0] Hsyncs per Vsync MSBs
This register contains the 8 MSBs of the 12-bit counter that
reports the number of Hsyncs per Vsync on the active input. It
is useful for determining the mode and is an aid in setting the
PLL divide ratio.
0x27—Bits[7:4] Hsyncs per Vsync LSBs
This register contains the four LSBs of the 12-bit counter that
reports the number of Hsyncs per Vsync on the active input.
TEST REGISTERS
0x28—Bits[7:0] Test Register 1
Must be written to 0xBF for proper operation.
0x29—Bits[7:0] Test Register 2
Must be written to 0x02 for proper operation.
0x2A—Bits[7:0] Test Register 3
Read only bits for future use.
0x2B—Bits[7:0] Test Register 4
Read only bits for future use.
0x2C—Bits[7:5] Offset Hold
Must be written to default 0x00 for proper operation.
0x2C—Bit[4] Auto-Offset Hold
This bit controls whether the auto-offset function runs
continuously or only once and holds the result. Continuous
updates are recommended because they allow the AD9984A to
compensate for drift over time, temperature, and so on. If one-
time updates are preferred, they should be performed every
time the part is powered up and when there is a mode change.
To perform a one-time update, auto-offset must first be enabled
(Register 0x1B, Bit 5). Next, this bit (auto-offset hold) must first
be set to 0 to let the auto-offset function operate and settle to a
final value. Auto-offset hold should then be set to 1 to hold the
offset values that the auto circuitry calculates. The AD9984A
auto-offset circuit’s maximum settle time is 10 updates. For
example, if the update frequency is set to once every 192 Hsyncs,
the maximum settling time is 1920 Hsyncs (10 × 192 Hsyncs).
Table 77. Auto-Offset Hold Bit
Value Result
0 Allows auto-offset to continuously update.
1 Disables auto-offset updates and holds the current
auto-offset values.
0x2C—Bits[3:0]
Must be written to 0x0 for proper operation.
0x2D—Bits[7:0] Test Register 5
Read/write bits for future use. Must be written to 0xE8 for
proper operation.
AD9984A
Rev. 0 | Page 39 of 44
0x2E—Bits[7:0] Test Register 6
Read/write bits for future use. Must be written to 0xE0 for
proper operation.
0x34—Bit[2] SOG Filter Enabler
When this bit is set to 1, the SOG does not pass pulses less than
250 ns in width. This reduces spurious signals that can improperly
drive the PLL circuit. Default for this bit is 0 or off.
0x36—Bit[0] VCO Gear Select
This bit allows the VCO to select a lower gear to run lower pixel
clocks while remaining in a more linear range.
Table 78. VCO Gear Select Bit
Value Result
0 Normal VCO setting.
1 Enables lower VCO clock output.
0x3C—Bits[7:4] Test Bits
Must be set to 0x0 for proper operation.
0x3C—Bit[3] Auto Gain Matching Hold
This bit controls whether the auto gain matching function runs
continuously or runs once and holds the result. Continuous
updates are recommended because they allow the AD9984A to
compensate for drift over time, temperature, and so on.
If one-time updates are preferred, they should be performed
every time the part is powered up and when there is a mode
change. To perform a one-time update, auto gain matching
must first be enabled (Register 0x3C, Bits[2:0]). Next, this bit
(auto gain matching hold) must first be set to 1 to let the auto
gain matching function operate and settle to a final value.
The auto gain matching hold bit should then be set to 0 to hold
the gain values that the auto circuitry calculates. The AD9984A
auto gain matching circuit’s maximum settle time is 10 updates.
For example, if the update frequency is set to once every 64 Hsyncs,
the maximum settling time would be 640 Hsyncs (10 × 64 Hsyncs).
Table 79. Auto Gain Matching Hold Bit
Value Result
01Disables auto gain updates and holds the current
auto gain values.
1 Allows auto gain to update continuously.
1The power-up default setting is 0.
0x3C—Bits[2:0] Auto Gain Matching Enable
These bits enable or disable the auto gain matching function.
Table 80. Auto Gain Matching Enable Bits
Value Result
000 Auto gain matching disabled.
110 Auto gain matching enabled.
AD9984A
Rev. 0 | Page 40 of 44
PCB LAYOUT RECOMMENDATIONS
The AD9984A is a high precision, high speed, analog device. To
achieve the maximum performance from the part, it is important
to have a well laid-out board. The section provides a guide for
designing a board using the AD9984A.
ANALOG INTERFACE INPUTS
Use the following layout techniques on the graphics inputs:
• Minimize the trace length running into the graphics
inputs. This is accomplished by placing the AD9984A as
close as possible to the graphics VGA connector. Long
input trace lengths are undesirable because they pick up
noise from the board and other external sources.
• Place the 75 Ω termination resistors (see Figure 4) as close
as possible to the AD9984A chip. Any additional trace
length between the termination resistors and the input of
the AD9984A increases the magnitude of reflections,
which corrupts the graphics signal.
• Use 75 Ω matched impedance traces. Trace impedances
other than 75 Ω also increase the chance of reflections.
• The AD9984A has a very high input bandwidth (300 MHz).
While desirable for acquiring a high resolution PC graphics
signal with fast edges, it also means that it captures any
high frequency noise. Therefore, it is important to reduce
the amount of noise that is coupled to the inputs. Avoid
running any digital traces near the analog inputs.
• Due to the high bandwidth of the AD9984A, using a low-
pass filter with the analog inputs can help to reduce noise.
(for many applications, filtering is unnecessary.) Experiments
have shown that placing a ferrite bead (specifically, the
Fair-Rite 2508051217Z0) in series prior to the 75 Ω
termination resistor is helpful in filtering excess noise.
However, an application could work best with a different
bead value. Alternatively, placing a 100 Ω to 120 Ω resistor
between the 75 Ω termination resistor and the input
coupling capacitor is beneficial.
Power Supply Bypassing
It is recommended to bypass each power supply pin with a
0.1 μF capacitor. An exception is when two or more supply pins
are adjacent to each other. For these groupings of powers/grounds,
it is only necessary to have one bypass capacitor. The fundamental
idea is to have a bypass capacitor within ~0.5 cm of each power
pin. Also, avoid placing the capacitor on the opposite side of the
PC board from the AD9984A, because doing so interposes
resistive vias in the path.
The bypass capacitors should be physically located between the
power plane and the power pin. Current should flow from the
power plane to the capacitor to the power pin. Do not make the
power connection between the capacitor and the power pin.
Placing a via underneath the capacitor pads, down to the power
plane, is generally the best approach.
It is particularly important to maintain low noise and good stability
of the PVD (the clock generator supply). Abrupt changes in PVD can
result in similar changes in sampling clock phase and frequency.
This can be avoided by paying careful attention to regulation,
filtering, and bypassing. It is desirable to provide separate regulated
supplies for each of the analog circuitry groups (VD and PVD).
Some graphic controllers use substantially different levels of
power when active (during active picture time), and when idle
(during horizontal and vertical sync periods). This can result in
a measurable change in the voltage supplied to the analog
supply regulator, which can in turn produce changes in the
regulated analog supply voltage. This can be mitigated by
regulating the analog supply, or at least PVD, from a different,
cleaner, power source (for example, from a 12 V supply).
It is also recommended to use a single ground plane for the
entire board. Experience has repeatedly shown that noise
performance is the same or better with a single ground plane.
Using multiple ground planes can be detrimental because each
separate ground plane is smaller, and long ground loops can result.
In some cases, using separate ground planes is unavoidable. For
these cases, place at least a single ground plane under the part.
The location of the split should be at the receiver of the digital
outputs. In this case, it is even more important to place components
wisely because the current loops become much longer (current
takes the path of least resistance). An example of a current loop
is power plane to AD9984A to digital output trace, to digital
data receiver, to digital ground plane, to analog ground plane.
PLL
Place the PLL loop filter components as close to the FILT pin as
possible. Do not place any digital or other high frequency traces
near these components. Use the values suggested in the data
sheet with 10% tolerances or less.
OUTPUTS (BOTH DATA AND CLOCKS)
Try to minimize the trace length that the digital outputs have to
drive. Longer traces have higher capacitance and require more
instantaneous current to drive, which creates more internal
digital noise. Shorter traces reduce the possibility of reflections.
Adding a series resistor of 50 Ω to 200 Ω can suppress reflections,
reduce EMI, and reduce the current spikes inside of the AD9984A.
If series resistors are used, place them as close to the AD9984A
pins as possible (although try not to add vias or extra length to
the output trace to get the resistors closer).
If possible, limit the capacitance driven by each digital output to
less than 10 pF. This is easily accomplished by keeping traces
short and connecting the outputs to only one device. Loading
the outputs with excessive capacitance increases the current
transients inside of the AD9984A and creates more digital noise
on its power supplies.
AD9984A
Rev. 0 | Page 41 of 44
DIGITAL INPUTS
Digital inputs on the AD9984A (HSYNC0, HSYNC1, VSYNC0,
VSYNC1, SOGIN0, SOGIN1, SDA, SCL, and CLAMP) are
designed to work with 3.3 V signals, but are tolerant of 5 V
signals. Therefore, no extra components need to be added if
using 5 V logic.
Any noise that gets onto the Hsync input trace adds jitter to the
system. Therefore, minimize the trace length and do not run
any digital or other high frequency traces near it.
Reference Bypass
The AD9984A has two reference voltages that must be bypassed
for proper operation of the ADC. REFLO and REFHI are
connected to each other through a 10 μF capacitor. These
references are used by the ADC circuitry to assure the greatest
stability. Place them as close to the AD9984A pin as possible.
AD9984A
Rev. 0 | Page 42 of 44
OUTLINE DIMENSIONS
COMP LIANT TO JE DE C S TANDARDS M S - 026-BEC
1.45
1.40
1.35
0.15
0.05
0.20
0.09
0.10
COPLANARITY
VIEW A
ROTATED 90° CCW
SEATING
PLANE
7°
3.5°
0°
6160
180
20 41
21 40
VIEW A
1.60
MAX
0.75
0.60
0.45
16.20
16.00 S Q
15.80
14.20
14.00 S Q
13.80
0.65
BSC
LEAD PITCH
0.38
0.32
0.22
TOP VI EW
(PINS DOWN)
PIN 1
051706-A
Figure 20. 80-Lead Low Profile Quad Flat Package [LQFP]
(ST-80-2)
Dimensions shown in millimeters
PIN 1
INDICATOR
TOP
VIEW 8.75
BSC SQ
9.00
BSC SQ
1
64
16
17
49
48
32
33
0.50
0.40
0.30
0.50 BSC 0.20 REF
12° MAX 0.80 MA X
0.65 TYP
1.00
0.85
0.80
7.50
REF
0.05 MAX
0.02 NOM
0.60 M A X
0.60 MAX
*4.85
4.70 SQ
4.55
EXPOSED PAD
(BOTTOM VIEW)
*COMP LI ANT TO JEDE C S TANDARDS MO-220-V M MD-4
EXCEPT FOR EXPOSED PAD DIMENSION
063006-B
SEATING
PLANE
PIN 1
INDICATOR
0.30
0.25
0.18
Figure 21. 64-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
9 mm x 9 mm Body, Very Thin Quad
(CP-64-1)
Dimensions shown in millimeters
ORDERING GUIDE
Model Temperature Range Package Description Package Option
AD9984AKSTZ-14010°C to 70°C 80-Lead Low Profile Quad Flat Package [LQFP] ST-80-2
AD9984AKSTZ-17010°C to 70°C 80-Lead Low Profile Quad Flat Package [LQFP] ST-80-2
AD9984AKCPZ-14010°C to 70°C 64-Lead Lead Frame Chip Scale Package [LFCSP_VQ] CP-64-1
AD9984AKCPZ-17010°C to 70°C 64-Lead Lead Frame Chip Scale Package [LFCSP_VQ] CP-64-1
AD9984A/PCBZ1 Evaluation Board [LQFP]
1 Z = RoHS Compliant Part.
AD9984A
Rev. 0 | Page 43 of 44
NOTES
AD9984A
Rev. 0 | Page 44 of 44
NOTES
Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent
Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips.
©2007 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D06476-0-7/07(0)
