P2781/82/84
General Purpose EMI
Reduction IC
©2010 SCILLC. All rights reserved. Publication Order Number:
NOVEMBER 2010 – Rev. 2.1 P2781/82/84
Features
• Provides up to 15dB of EMI suppression
• FCC approved method of EMI attenuation
• Generates a 1X, 2X, and 4X low EMI spread spectrum
clock of the input frequency
• Input frequency range from 3 to 78MHz
• External loop filter for spread % adjustment
• Spreading ranges from ±0.25% to ±5.0%
• Ultra low cycle-to-cycle jitter
• Zero-cycle slip
• 3.3V operating voltage range
• Ultra-low power CMOS design
• P278xA is available in an 8 pin SOIC Package
Product Description
The P278xA is a versatile spread spectrum frequency
modulator designed specifically for digital camera and other
digital video and imaging applications. The P278xA
reduces electromagnetic interference (EMI) at the clock
source, which provides system wide reduction of EMI of all
clock dependent signals. The P278xA allows significant
system cost savings by reducing the number of circuit
board layers and shielding that are traditionally required to
pass EMI regulations.
The P278xA uses the most efficient and optimized
modulation profile approved by the FCC. The P278xA
modulates the output of a single PLL in order to “spread”
the bandwidth of a synthesized clock and, more
importantly, decreases the peak amplitudes of its
harmonics. This result in significantly lower system EMI
compared to the typical narrow band signal produced by
oscillators and most frequency generators. Lowering EMI
by increasing a signal’s bandwidth is called spread
spectrum clock generation.
Applications
The P278xA is targeted towards MFP, xDSL, fax modem,
set-top box, USB controller, DSC, and embedded systems.
Block Diagram
Crystal
Oscillator
Frequency
Divider
Feedback
Divider
Phase
Detector
Modulation
Output
Divider
VCO
XIN / CLKIN
XOUT
FS0 FS1 LF VDD
VSS
PLL
ModOUT
P2781/82/84
Rev. 2 | Page 2 of 8 | www.onsemi.com
Pin Configuration
Pin Description (P278xA)
Pin#
Pin Name Type Description
1 XIN/CLKIN I Connect to crystal or clock input. This pin has dual functions. It can be connected
either to an external crystal or an external reference clock.
2 XOUT O Crystal connection. If using an external reference, this pin must be left
unconnected.
3 FS1 I Digital logic input used to select input frequency range (see the Input Frequency
Selection Table). This pin has an internal pull-up resistor.
4 LF I
External Loop Filter for the PLL. By changing the value of the CRC circuit, the
percentage spread can be adjusted accordingly. See the Loop Filter Selection
Table for detail value.
5 VSS I Ground Connection. Connect to system ground.
6 ModOUT O Spread Spectrum Clock Output.
7 FS0 I Digital logic input used to select input frequency range (see the Input Frequency
Selection Table). This pin has an internal pull-up resistor.
8 VDD P Connect to +3.3 V
Input Frequency Selection Table
FS1 FS0 Input (MHz) Output Frequency Scaling (MHz) Modulation Rate (KHz)
P2781A P2782A P2784A
0 0 3 to 9 3 to 9 6 to 18 12 to 36 Fin / 128
0 1 10 to 19 10 to 19 20 to 38 40 to 76 Fin / 256
1 0 20 to 38 20 to 38 40 to 76 80 to 152 Fin / 512
1 1 39 to 78 39 to 78 78 to 156 156 to 312 Fin / 1024
Standard pin Configuration offered in both
8 pin SOIC Packages.
FS1
LF
FS0
VDD
VSS
1
2
3
4
5
6
7
8
P278xA
XIN / CLKIN
ModOUT
XOUT
P2781/82/84
Rev. 2 | Page 3 of 8 | www.onsemi.com
Loop Filter Selection Table VDD 3.3V
Contact ON Semiconductor for loop values that are not listed in the table and for
Component selection values for industrial and automotive temperatures.
Input
MHz FS1
FS0
BW = ±0.50%
1
BW = ±0.75%
1
BW = ±1.00%
1
BW = ±1.25%
1
C1
(pF) C2
(pF) R1
(ohm)
C1
(pF) C2
(pF) R1
(ohm)
C1
(pF) C2
(pF) R1
(ohm) C1
(pF) C2
(pF) R1
(ohm)
3 0 0 270 330,000
220 270 330,000
300 270 100,000
390 560 100,000 510
4 0 0 270 100,000
270 270 100,000
390 270 100,000
560 560 100,000 680
5 0 0 270 100,000
390 270 100,000
560 270 100,000
750 560 100,000 910
6 0 0 270 100,000
510 270 100,000
750 270 10,000 1,000 680 6,800 1,200
7 0 0 270 100,000
620 270 100,000
1,000
270 5,600 1,200 330 3,300 1,200
8 0 0 270 100,000
820 270 100,000
1,200
270 12,000 2,200 680 6,800 2,200
9 0 0 270 100,000
1,000
270 100,000
1,500
270 5,600 2,200 270 2,700 2,200
10 0 1 270 100,000
330 270 100,000
510 270 100,000
750 560 100,000 910
11 0 1 270 100,000
390 270 100,000
560 270 100,000
866(1%)
560 100,000 1,100
12 0 1 270 100,000
510 270 100,000
750 270 10,000 1,000 680 6,800 1,200
13 0 1 270 100,000
560 270 100,000
820 270 12,000 1,200 470 4,700 1,200
14 0 1 270 100,000
620 270 100,000
1,000
270 5,600 1,200 330 3,300 1,200
15 0 1 270 100,000
750 270 100,000
1,100
270 3,900 1,200 330 3,300 1,500
16 0 1 270 100,000
820 270 100,000
1,200
270 12,000 2,200 680 6,800 2,200
17 0 1 270 100,000
910 270 100,000
1,300
270 10,000 2,200 390 3,900 2,200
18 0 1 270 100,000
1,000
270 100,000
1,500
270 5,600 2,200 270 2,700 2,200
19 0 1 270 100,000
1,200
270 100,000
1,600
270 3,300 2,200 270 2,700 2,700
20 0 0 270 100,000
330 270 100,000
560 270 100,000
750 560 100,000 910
21-22
1 0 270 100,000
390 270 100,000
620 270 100,000
866 (1%)
560 100,000 1,100
23-24
1 0 270 100,000
510 270 100,000
750 270 10,000 1,000 680 6,800 1,200
25-26
1 0 270 100,000
560 270 100,000
820 270 12,000 1,200 470 4,700 1,200
27-28
1 0 270 100,000
620 270 100,000
1,000
270 6,800 1,200 330 3,300 1,200
29-30
1 0 270 100,000
750 270 100,000
1,100
270 3,900 1,200 330 3,300 1,500
31-32
1 0 270 100,000
820 270 100,000
1,200
270 12,000 2,200 680 6,800 2,200
33-34
1 0 270 100,000
910 270 100,000
1,300
270 10,000 2,200 390 3,900 2,200
35-36
1 0 270 100,000
1,000
270 100,000
1,500
270 5,600 2,200 270 2,700 2,200
37-38
1 0 270 100,000
1,200
270 100,000
1,600
270 3,300 2,200 270 2,700 2,700
39-42
1 1 270 100,000
330 270 100,000
560 270 100,000
750 560 100,000 910
43-46
1 1 270 100,000
390 270 100,000
620 270 100,000
866 (1%)
560 100,000 1,100
47-50
1 1 270 100,000
510 270 100,000
750 270 10,000 1,000 680 6,800 1,200
51-54
1 1 270 100,000
560 270 100,000
820 270 12,000 1,200 470 4,700 1,200
55-58
1 1 270 100,000
620 270 100,000
1,000
270 6,800 1,200 330 3,300 1,200
59-62
1 1 270 100,000
750 270 100,000
1,100
270 3,900 1,200 330 3,300 1,500
63-66
1 1 270 100,000
820 270 100,000
1,200
270 12,000 2,200 680 6,800 2,200
67-70
1 1 270 100,000
910 270 100,000
1,300
270 8,200 2,200 390 3,900 2,200
71-74
1 1 270 100,000
1,000
270 100,000
1,600
270 5,600 2,200 270 2,700 2,200
75-78
1 1 270 100,000
1,200
270 100,000
1,800
270 3,300 2,200 270 2,700 2,700
Note: 1. The BW value is representative of typical conditions.
P2781/82/84
Rev. 2 | Page 4 of 8 | www.onsemi.com
Spread Spectrum Selection
The P278xA performs Zero Cycle Slip when set at low percentage spreading. This allows no occurrence of system timing
error. The optimal setting should minimize system EMI to the fullest without affecting system performance. The spreading is
described as a percentage deviation of the center frequency.
(Note: the center frequency is the frequency of the external reference input on CLKIN, Pin 1.)
The P2781A is designed for PC peripheral, networking, notebook PC, and LCD monitor applications. It is optimized for
operation between 3 to 78MHz range. In the following application schematic example, the P2781A spread percentage
selection is determined by the external LF value specified in the Loop Filter Selection Table. The Input Frequency Selection
Table specifies the input frequency range. The external LF allows the user to fine tune the spread percentage to optimize the
EMI reduction benefits of the spread spectrum.
Note: Both logic input pins FS1 and FS0 have to be connected to either VDD or VSS. Do not leave them floating.
1
2
3
4
8
7
6
5
VDD
FS0
ModOUT
VSS
LF
FS1
XOUT
XIN/CLKIN
P2
78xA
+3.3V
Modulated 16MHz Clock
To target Chip
16 MHz
0.1µF
C2
C1
R1
0 Ohm
2.2 K
P2781/82/84
Rev. 2 | Page 5 of 8 | www.onsemi.com
Absolute Maximum Ratings
Symbol Parameter Rating Unit
V
DD
, V
IN
Voltage on any pin with respect to Ground -0.5 to +4.6 V
T
STG
Storage temperature -65 to +125 °C
T
s
Max. Soldering Temperature (10 sec) 260 °C
T
J
Junction Temperature 150 °C
T
DV
Static Discharge Voltage (As per JEDEC STD22- A114-B) 2 KV
Note: These are stress ratings only and are not implied for functional use. Exposure to absolute maximum ratings for prolonged periods of time may affect
device reliability.
Operating Conditions
Parameter Description Min Max Unit
VDD Supply Voltage 3.0 3.6 V
T
A
Operating Temperature (Ambient Temperature) -40 +85 °C
C
L
Load Capacitance 15 pF
C
IN
Input Capacitance 7 pF
DC Electrical Characteristics
(Test condition: All parameters are measured at room temperature (+25°C) unless otherwise stated.)
Symbol
Parameter Min Typ Max Unit
V
IL
Input low voltage VSS – 0.3 0.8 V
V
IH
Input high voltage 2.0 VDD +0.3 V
I
IL
Input low current
(internal input pull-up resistor on FS0 and FS1) 60 µA
I
IH
Input high current
(internal input pull-up resistor on FS0 and FS1) 60 µA
I
XOL
XOUT output low current 10 mA
I
XOH
XOUT output high current 10 mA
V
OL
Output low voltage (VDD = 3.3V, I
OL
= 20mA) 0.4 V
V
OH
Output high voltage (VDD = 3.3V, I
OH
= 20mA) 2.5 V
I
DD
Static supply current 3 mA
I
CC
Typical dynamic supply current
(25pF scope probe loading) 5.2 at 3MHz 21.2 at 82MHz
mA
VDD Operating voltage 3.0 3.3 3.6 V
P2781/82/84
Rev. 2 | Page 6 of 8 | www.onsemi.com
AC Electrical Characteristics
Symbol
Parameter Min Typ Max Unit
f
IN
Input frequency: P278xA 3 78
MHz
f
OUT
Output frequency:
P2781A 3 78
P2782A 6 156
P2784A 12 312
t
LH
P278xA Output rise time (measured at 0.8V to 2.0V,
25pF scope probe loading) 1 nS
t
HL
P278xA Output fall time (measured at 2.0V to 0.8V, 25
pF scope probe loading) 1 nS
t
JC
P2781A Jitter (cycle-to-cycle, ±6sigma, 1000 sweeps,
±0.5% spread, I/O frequency = 16MHz) ±250 pS
t
D
P2781A Output duty cycle deviation (error from 50%
duty cycle, 25pF scope probe loading) ±1 @ 3MHz ±2 @ 82MHz %
∆F P278xA Frequency deviation tolerance from BW%
stated in the Loop Filter Selection Table -20 0 +20 %
P2781/82/84
Rev. 2 | Page 7 of 8 | www.onsemi.com
Package Information
8-Pin SOIC Package
D
EH
D
A1
A2
A
θ
L
C
B
e
Symbol
Dimensions
Inches Millimeters
Min Max Min Max
A1 0.004 0.010 0.10 0.25
A 0.053 0.069 1.35 1.75
A2 0.049 0.059 1.25 1.50
B 0.012 0.020 0.31 0.51
C 0.007 0.010 0.18 0.25
D 0.193 BSC 4.90 BSC
E 0.154 BSC 3.91 BSC
e 0.050 BSC 1.27 BSC
H 0.236 BSC 6.00 BSC
L 0.016 0.050 0.41 1.27
θ 0° 8° 0° 8°
Note: Controlling dimensions are millimeters.
SOIC - 0.074 grams unit weight.
P2781/82/84
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without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular
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including without limitation special, consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or
specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be
validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others.
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intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death
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For additional information, please contact your
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Ordering Codes
Ordering # Top Marking Package Type Temperature
P2781AF-08ST ABG 8 PIN SOIC, TUBE, Pb Free 0°C to + 70°C
P2781AF-08SR ABG 8 PIN SOIC, TAPE AND REEL,Pb Free 0°C to +70°C
I2781AF-08ST ABH 8 PIN SOIC, TUBE, Pb Free -40°C to +85°C
I2781AG-08SR ABJ 8 PIN SOIC, TAPE AND REEL, Green -40°C to +85°C
P2782AF-08SR ABK 8 PIN SOIC, TAPE AND REEL,Pb Free 0°C to +70°C
P2784AF-08SR ABO 8 PIN SOIC, TAPE AND REEL,Pb Free 0°C to +70°C
A “microdot” placed at the end of last row of marking or just below the last row toward the center of package indicates Pb-free.
