Figure 1. ADS-949 Functional Block Diagram
FEATURES
14-bit resolution
12.8MHz minimum sampling rate
No missing codes over full military temperature range
Ideal for both time and frequency-domain applications
Excellent THD (–81dB) and SNR (78dB)
Edge-triggered
Small, 32-pin, ceramic DDIP or SMT
Low-power, 2 Watts
Low cost
GENERAL DESCRIPTION
The low-cost ADS-949 is a 14-bit, 12.8MHz sampling A/D
converter. This device accurately samples full-scale input
signals up to Nyquist frequencies with no missing codes.
Excellent differential nonlinearity error (DNL), signal-to-noise
ratio (SNR), and total harmonic distortion (THD) make the
ADS-949 the ideal choice for both time-domain (CCD/FPA
imaging, scanners, process control) and frequency-domain
(radar, telecommunications, spectr um analysis) applications.
The functionally complete ADS-949 contains a fast-settling
sample/hold amplifier, a subranging A/D conver ter, an internal
reference, timing/control logic, and error-correction circuitry.
Digital input and output levels are TTL. The ADS-949 only
requires the rising edge of a start convert pulse to operate.
Requiring only +15V, +5V and –5V supplies, the ADS-949
typically dissipates just 2 Watts. The device is offered with a
Bipolar input range of ±2.5V and Unipolar range of 0 to 5 volts.
Models are available for use in either commercial (0 to +70°C)
or military (–55 to +125°C) operating temperature ranges.
®®
A proprietary, auto-calibrating, error-correcting circuit allows
the device to achieve specified performance over the full
military temperature range.
INPUT/OUTPUT CONNECTIONS
PIN FUNCTION PIN FUNCTION
1 VIN A 32 RANGE
2 VIN B 31 GAIN ADJUST
35V 30 +5V ANALOG
4 OFFSET ADJ. 29 ANALOG GND
5 RANGE REF. 28 +15V
6 2.5V REF. 27 +5V DIGITAL
7 START CONVERT 26 DIGITAL GND
8 EOC 25 OVERFLOW
9 ENABLE 24 MSB
10 BIT 14 (LSB) 23 BIT 1 (MSB)
11 BIT 13 22 BIT 2
12 BIT 12 21 BIT 3
13 BIT 11 20 BIT 4
14 BIT 10 19 BIT 5
15 BIT 9 18 BIT 6
16 BIT 8 17 BIT 7
ADS-949
14-Bit, 12.8MHz
Sampling A/D Converters
DATEL, Inc., Mansfield, MA 02048 (USA) Tel: (508)339-3000, (800)233-2765 Fax: (508)339-6356 E-mail: sales@datel.com Internet: www .datel.com
REF DAC
REGISTER
REGISTER
OUTPUT REGISTER
10 BIT 14 (LSB)
11 BIT 13
12 BIT 12
13 BIT 11
14 BIT 10
15 BIT 9
16 BIT 8
17 BIT 7
18 BIT 6
19 BIT 5
20 BIT 4
21 BIT 3
22 BIT 2
23 BIT 1 (MSB)
24 MSB
TIMING AND
CONTROL LOGIC
OFFSET ADJUST 4
VIN A 1
START CONVERT 7
EOC 8
GAIN ADJUST 31
+5V ANALOG SUPPLY 30
+5V DIGITAL SUPPLY 27
V RANGE 32
5.2V SUPPLY 3
+15V SUPPLY 28
ANALOG GROUND 29
DIGITAL GROUND 26
+S/H
BUFFER
DIGITAL CORRECTION LOGIC
FLASH
ADC
1
FLASH
ADC
2
POWER AND GROUNDING
5
AMP
9 ENABLE
25 OVERFLOW
VIN B 2
2.5 V REF 6
ADS-949
2
®®
+25°C 0 to +70°C –55 to +125°C
ANALOG INPUT MIN. TYP. MAX. MIN. TYP. MAX. MIN. TYP. MAX. UNITS
Bipolar Input Voltage Range
±1 ±2.5 ±1 ±2.5 ±1 ±2.5 Volts
Unipolar Input Voltage Range
0 to 2 0 to 5 0 to 2 0 to 5 0 to 2 0 to 5 Volts
Input Resistance (Vin A) 400 ——400 ——400
Input Capacitance 615615615pF
DIGITAL INPUT
Logic Levels
Logic "1" +2.0 ——+2.0 ——+2.0 ——Volts
Logic "0" ——+0.8 ——+0.8 ——+0.8 Volts
Logic Loading "1" ——+20 ——+20 ——+20 µA
Logic Loading "0" ——20 ——20 ——20 µA
Start Convert Positive Pulse Width
50 ——50 ——50 ns
STATIC PERFORMANCE
Resolution 14 ——14 ——14 Bits
Integral Nonlinearity ±0.75 ——±0.75 ——±1 LSB
Differential Nonlinearity (fin = 10kHz) 0.95 ±0.5 +1.25 0.95 ±0.5 +1.25 0.95 ±0.5 +1.5 LSB
Full Scale Absolute Accuracy ±0.15 ±0.4 ±0.15 ±0.4 ±0.4 ±0.8 %FSR
Bipolar Zero Erro r (Tech Note 2) ±0.1 ±0.3 ±0.1 ±0.3 ±0.3 ±0.6 %FSR
Gain Error (Tech Note 2) ±0.2 ±0.4 ±0.2 ±0.4 ±0.4 ±1.5 %
No Missing Codes (fin = 10kHz) 14 ——14 ——14 ——Bits
DYNAMIC PERFORMANCE
Peak Harmonics (0.5dB)
dc to 1MHz —–83 76 —–83 75 —–79 71 dB
1MHz to 2.5MHz —–78 72 —–78 72 —–73 68 dB
2.5MHz to 5MHz —–76 71 —–76 71 —–71 65 dB
Total Harmonic Distortion (0.5dB)
dc to 1MHz —–81 74 —–81 74 —–77 70 dB
1MHz to 2.5MHz —–76 71 —–76 71 —–72 66 dB
2.5MHz to 5MHz —–74 69 —–74 69 —–69 63 dB
Signal-to-Noise Ratio
(w/o distortion, 0.5dB)
dc to 1MHz 72 78 72 78 70 78 dB
1MHz to 2.5MHz 72 77 72 77 70 77 dB
2.5MHz to 5MHz 72 76 72 76 70 76 dB
Signal-to-Noise Ratio
(& distortion, 0.5dB)
dc to 1MHz 70 77 70 74 68 73 dB
1MHz to 2.5MHz 70 74 70 74 66 71 dB
2.5MHz to 5MHz 69 73 69 73 65 70 dB
Noise 150 ——150 ——150 µVrms
Two-tone Intermodulation
Distortion (fin = 2.45MHz,
1.975MHz, fs = 10MHz, 0.5dB) —–82 ——82 ——82 dB
Input Bandwidth (3dB)
Small Signal (20dB input) 30 ——30 ——30 MHz
Large Signal (0.5dB input) 20 ——20 ——20 MHz
Feedthrough Rejection (fin = 5MHz) 85 ——85 ——85 dB
Slew Rate ±400 ——±400 ——±400 V/µs
Aperture Delay Time +5 ——+5 ——+5 ns
Aperture Uncertainty 2—— 2——2ps rms
FUNCTIONAL SPECIFICATIONS
(TA = +25°C, +VDD = +5V, VDD = 5V, +Vcc = +15V, 12.8MHz sampling rate , ±2.5V input range, and a minimum 3 minute warmup
unless otherwise specified.)
PARAMETERS MIN. TYP. MAX. UNITS
Operating Temp. Rang e , Case
ADS-949MC, GC 0 +70 °C
ADS-949MM, GM, 55 +125 °C
Thermal Impedance
θ
jc 6—°C/Watt
θ
ca 23 —°C/Watt
Storage T emperature Range 65 +150 °C
Package Type 32-pin, metal-sealed, ceramic DDIP or SMT
Weight 0.46 ounces (13 grams)
ABSOLUTE MAXIMUM RATINGS
PARAMETERS LIMITS UNITS
+5V Supply (Pins 27, 30) 0 to +6 Volts
+15V Supply (Pin 28) 0 to +16 Volts
5V Supply (Pin 3) 0 to 5.5V Volts
Digital Input (Pin 7) 0.3 to +VDD +0.3 Volts
Analog Input (Pins 1, 2) ±5 Volts
Lead Temperature (10 seconds) +300 °C
PHYSICAL/ENVIRONMENTAL
ADS-949
3
®®
+25°C 0 to +70°C55 to +125°C
DYNAMIC PERFORMANCE
(Cont.)
MIN. TYP. MAX. MIN. TYP. MAX. MIN. TYP. MAX. UNITS
S/H Acquisition Time
( to ±0.003%FSR, 5V step) 40 45 40 45 40 45 ns
Overvoltage Recovery Time ——100 ——100 ——100 ns
A/D Conversion Rate 12.8 ——12.8 ——12.8 ——MHz
DIGITAL OUTPUTS
Logic Levels
Logic "1" +2.4 ——+2.4 ——+2.4 ——Volts
Logic "0" ——+0.4 ——+0.4 ——+0.4 Volts
Logic Loading "1" ——–4——4—— 4mA
Logic Loading "0" ——+4 ——+4 —— +4 mA
Output Coding Straight Binary, Offset Binary
POWER REQUIREMENTS
Power Supply Ranges
+5V Supply +4.75 +5.0 +5.25 +4.75 +5.0 +5.25 +4.9 +5.0 +5.25 Volts
5.2V Supply 4.75 5.2 5.45 4.75 5.2 5.45 4.9 5.2 5.45 Volts
+15V Supply +14.5 +15 +15.5 +14.5 +15 +15.5 +14.5 +15 +15.5 Volts
Power Supply Currents
+5V Supply +250 +260 +250 +260 +250 +260 mA
5.2V Supply —–200 210 —–200 210 —–200 210 mA
+15V Supply +14.5 +15 +15.5 +14.5 +15 +15.5 +14.5 +15 +15.5 Volts
Power Dissipation 2.0 2.25 2.0 2.25 2.0 2.25 Watts
Power Supply Rejection ——±0.1 ——±0.1 ——±0.1 %FSR/%V
Footnotes:
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-949
requires careful attention to pc card layout and power
supply decoupling. The devices analog and digital ground
systems are connected to each other internally. For optimal
performance, tie all ground pins (26 and 29) directly to a
large analog ground plane beneath the package.
Bypass all power supplies to ground with 4.7µF tantalum
capacitors in parallel with 0.1µF ceramic capacitors. Locate
the bypass capacitors as close to the unit as possible.
2. The ADS-949 achieves its specified accuracies without the
need for external calibration. It is recommended that the
+5VA and +5VD supplies should be powered up from the
same source. If required, the devices small initial offset and
gain errors can be reduced to zero using the adjustment
circuitry shown in Figure 2,3.
When using this circuitry, or any similar offset and gain
calibration hardware, make adjustments following warmup.
To avoid interaction, always adjust offset before gain.
3. Applying a start convert pulse while a conversion is in
progress (EOC = logic 1) will initiate a new and inaccurate
conversion cycle. Data for the interrupted and subsequent
conversions will be invalid.
4. A passive bandpass filter is used at the input of the A/D for
all production testing.
All power supplies should be on before applying a start convert pulse. All
supplies and the clock (start convert pulses) must be present during warmup
periods. The device must be continuously converting during this time.
Contact DATEL for other input voltage ranges.
A 50ns wide start convert pulse is used for all production testing. For
applications requiring less than an 12.8MHz sampling rate, wider start con vert
pulses can be used.
Effective bits is equal to:
(SNR + Distortion) 1.76 + 20 log Full Scale Amplitude
Actual Input Amplitude
6.02
ADS-949
4
®®
CALIBRATION PROCEDURE
Any offset and/or gain calibration procedures should not be
implemented until devices are fully war med up. To avoid
interaction, offset must be adjusted before gain. The ranges of
adjustment for the circuits in Figures 2 and 3 are guaranteed to
compensate for the ADS-949s initial accuracy errors and may
not be able to compensate for additional system errors.
A/D converters are calibrated by positioning their digital
outputs exactly on the transition point between two adjacent
digital output codes. This can be accomplished by connecting
LEDs to the digital outputs and adjusting until certain LEDs
flicker equally between on and off. Other approaches employ
digital comparators or microcontrollers to detect when the
outputs change from one code to the next.
Offset adjusting for the ADS-949 is normally accomplished at
the point where the MSB is a 1 and all other output bits are 0s
and the LSB just changes from a 0 to a 1. This digital output
transition ideally occurs when the applied analog input is
+½ LSB (+153µV).
Gain adjusting is accomplished when all bits are 1s and the
LSB just changes from a 1 to a 0. This transition ideally occurs
when the analog input is at +full scale minus 1½ LSB's
(+2.49954V).
Zero/Offset Adjust Procedure
1. Apply a train of pulses to the START CONVERT input (pin
7) so the converter is continuously converting.
2. Apply +153µV to the ANALOG INPUT (pin 1).
3. Adjust the offset potentiometer until the output bits are
10 0000 0000 0000 and the LSB flickers between 0 and 1.
Gain Adjust Procedure
1. Apply +2.49954V to the ANALOG INPUT (pin 1).
2. Adjust the gain potentiometer until all output bits are 1s and
the LSB flickers between 1 and 0.
3. To confirm proper operation of the device, vary the input
signal to obtain the output coding listed in Table 2.
INPUT VOLTAGE ZERO ADJUST GAIN ADJUST
RANGE +½ LSB +FS 1½ LSB
±2.5V +153µV +2.49954V
Table 1. Gain and Zero Adjust
Figure 2. Typical ADS-949 Bipolar Connection Diagram
0.1µF
4.7µF
27
+5VD
29
AGND
3
5V
ADS-949
20k
9
4.7µF
+5VA
26
DGND
5V
+5V
1VIN A
4 OFFSET ADJUST
7 START CONVERT
23
22
21
20
19
18
17
16
15
14
13
12
11
10
8
BIT 1 (MSB)
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14 (LSB)
EOC
BIPOLAR
ANALOG
INPUT
START
CONVERT
Bypass Pins 5, 6, 32, with a 4.7µF to Analog Ground.
Note: The Voltage Value at Pin 32 (Range) sets the input voltage range of the ADS-949
eg: If Pin 6 (2.5 V R e fere n ce O u t) is tie d to th e R a ng e P in 32 (2 0 k Pot is shorted), then
the input range of the ADS-949 becomes ±2.5V
If the 20k Pot is set at midrange then the input range of the ADS-949 becomes ±1.25V
+
ZERO/
OFFSET
ADJUST
5V
+5V
31 GAIN ADJUST
GAIN
A
DJUST
20K
5V
2 VIN B
9 ENABLE
20k
6 2.5V REF
32 RANGE
+15V
28
+15V
+5VD
4.7µF
+
30
+5VA
0.1µF 0.1µF
4.7µF
+
0.1µF
+
5 RANGE REF
ADS-949
5
®®
Electrically-insulating, ther mally-conductive "pads" may be
installed underneath the package. Devices should be soldered
to boards rather than socketed, and of course, minimal air flow
over the surface can greatly help reduce the package
temperature.
In more severe ambient conditions, the package/junction
temperature of a given device can be reduced dramatically
(typically 35%) by using one of DATEL's HS Series heat sinks.
See Ordering Information for the assigned par t number. See
page 1-183 of the DATEL Data Acquisition Components Catalog
for more information on the HS Series. Request DATEL
Application Note AN8, "Heat Sinks for DIP Data Converters",
or contact DATEL directly, for additional information.
THERMAL REQUIREMENTS
All DATEL sampling A/D converters are fully characterized
and specified over operating temperature (case) ranges of
0 to +70°C and 55 to +125°C. All room temperature
(TA = +25°C) production testing is performed without the use
of heat sinks or forced air cooling. Thermal impedance
figures for each device are listed in their respective
specification tables.
These devices do not normally require heat sinks, however,
standard precautionary design and layout procedures should
be used to ensure devices do not overheat. The ground and
power planes beneath the package, as well as all pcb signal
runs to and from the device, should be as heavy as possible
to help conduct heat away from the package.
Figure 3. Typical ADS-949 Unipolar Connection Diagram
0.1µF
4.7µF
27
+5VD
29
AGND
3
5V
ADS-949
20k
9
4.7µF
+5VA
26
DGND
5V
+5V
1VIN A
4 OFFSET ADJUST
7 START CONVERT
23
22
21
20
19
18
17
16
15
14
13
12
11
10
8
BIT 1 (MSB)
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 9
BIT 10
BIT 11
BIT 12
BIT 13
BIT 14 (LSB)
EOC
UNIPOLAR
ANALOG
INPUT
START
CONVERT
Bypass Pins 5, 6, 32 with a 4.7µF to Analog Ground.
Note: The Voltage Value at Pin 32 (Range) sets the input voltage range of the ADS-949
eg: If Pin 6 (2 .5V Reference O u t) is tie d to th e R an g e Pin 32 (20k Pot is s ho rted ), th e n
the input range of the ADS-949 becomes 0 to 5V
If the 20k Pot is set at midrange then the input range of the ADS-949 becomes 0 to 2.5V
+
ZERO/
OFFSET
ADJUST
5V
+5V
31 GAIN ADJUST
GAIN
A
DJUST
20K
5V
2 VIN B
9 ENABLE
20k
6 2.5V REF
32 RANGE
+15V
28
+15V
+5VD
4.7µF
+
30
+5VA
0.1µF 0.1µF
4.7µF
+
0.1µF
+
5
RANGE REF
Table 3. Output Coding
UNIPOLAR INPUT VOLT. OUTPUT CODING INPUT VOLT. BIPOLAR
SCALE 0 T O +5V MSB LSB MSB LSB ±2.5V SCALE
+FS 1 LSB +4.999695 11 1111 1111 1111 01 1111 1111 1111 +2.499695 +FS 1LSB
+7/8 FS +4.375000 11 1000 0000 0000 01 1000 0000 0000 +1.875000 +3/4FS
+3/4 FS +3.75000 11 0000 0000 0000 01 0000 0000 0000 +1.250000 +1/2FS
+1/2 FS +2.500000 10 0000 0000 0000 00 0000 0000 0000 0.000000 0
+1/4 FS +1.250000 01 0000 0000 0000 11 0000 0000 0000 1.250000 1/2FS
+1/8 FS +0.625000 00 1000 0000 0000 10 1000 0000 0000 1.875000 3/4FS
+1 LSB +0.000305 00 0000 0000 0001 10 0000 0000 0001 2.499695 FS+1LSB
0 0.000000 00 0000 0000 0000 10 0000 0000 0000 2.500000 FS
STRAIGHT BIN.
OFF. BINARY TWO'S COMP.
ADS-949
6
®®
Figure 5. FFT Analysis of ADS-949
(fs = 12.8MHz, fin = 3.85MHz, Vin = 0.5dB, 16,384 point FFT) Figure 6. ADS-949 Histogram
START
CONVERT
Minimum is 40ns
OUTPUT
DATA
ENABLED
EOC
N
Note: 1. Scale is approximately 10ns per division. All values are Typical.
DATA OUT
ENABLED
N+1
40ns
40ns
20ns
60ns
DATA N-3 DATA N-2 DATA N-1 DATA N
30ns
20ns
DATA N-3 DATA N-2 DATA N-1 DATA N
HZ HZ HZ HZ
Figure 7. ADS-949 Timing Diagram
ADS-949
7
®®
Figure 7. ADS-949 Evaluation Board Schematic (ADS-B949)
CONTACT DATEL FOR SCHEMATIC
ADS-949
DATEL, Inc. 11 Cabot Boulevard, Mansfield, MA 02048-1151
Tel: (508) 339-3000 (800) 233-2765 Fax: (508) 339-6356
Internet: www.datel.com E-mail:sales@datel.com
Data Sheet Fax Bac k: (508) 261-2857
D ATEL makes no representation that the use of its products in the circuits described herein, or the use of other technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein
do not imply the granting of licenses to mak e , use, or sell equipment constructed in accordance therewith. Specifications are subject to change without notice. The DATEL logo is a registered D ATEL, Inc. trademark.
DATEL (UK) LTD. Tadley, England Tel: (01256)-880444
DATEL S.A.R.L. Montigny Le Bretonneux, F rance Tel: 1-34-60-01-01
DATEL GmbH München, Germany Tel: 89-544334-0
DATEL KK Tokyo, Japan Tel: 3-3779-1031, Osaka Tel: 6-354-2025
DS-0434A 7/22/99
OPERATING 32-PIN
MODEL TEMP. RANGE P A CKAGE
ADS-949MC 0 to +70°C DDIP
ADS-949MM 55 to +125°C DDIP
ADS-949/883 55 to +125°C DDIP
ADS-949GC 0 to +70°C SMT
ADS-949GM 55 to +125°C SMT
ORDERING INFORMATION
ACCESSORIES
ADS-B949 Ev aluation Board (without ADS-949)
Receptacles for PC board mounting can be ordered through AMP, Inc., Part # 3-331272-8 (Component Lead
Socket), 32 required. For MIL-STD-883 product specifcation, contact DATEL.
®®
MECHANICAL DIMENSIONS
INCHES (mm)
ISO 9001
ISO 9001
REGISTERED
®®
1.62 MAX.
(41.15)
0.92 MAX.
(23.37)
0.018 TYP.
(0.46)
1.50 TYP
(38.10)
0.100 TYP.
(2.54)
0.05 TYP.
(1.27) 0.175 TYP
(4.45)
0.05 TYP.
(1.27)
0.220 TYP.
(6.86)
0.90 TYP.
(22.86)
0.010 TYP.
(0.254)
Dimension Tolerances
(unless otherwise indicated):
2 place decimal (.XX) ±0.010 (±0.254)
3 place decimal (.XXX) ±0.005 (±0.127)
Lead Material: Kovar Alloy
Lead Finish: 50 microinches (minimum)
gold plating over 100 microinches
(nominal) nickel plating
PIN 1 INDEX
0.05 TYP.
(
1.27
)
SEATING PLANE