Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
1 of 1 http://www.pulsecore.com
®
General Purpose EMI Reduction IC
FEATURES
• Provides up to 15 dB 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 78 MHz
• 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
• 10 mA output drives
• TTL or CMOS compatible outputs
• Ultra-low power CMOS design
• Available in 8 pin SOIC and TSSOP
PRODUCT DESCRIPTION
The P278xx is a versatile spread spectrum
frequency modulator designed specifically for
digital camera and other digital video and imaging
applications. The P278xx reduces
electromagnetic interference (EMI) at the clock
source, which provides system wide reduction of
EMI of all clock dependent signals. The P278xx
allows significant system cost savings by reducing
the number of circuit board layers and shielding
that are traditionally required to pass EMI
regulations.
The P278xx uses the most efficient and optimized
modulation profile approved by the FCC.
The P278xx 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 results 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 P278xx is targeted towards MFP, xDSL, fax
modem, set-top box, USB controller, DSC, and
embedded systems.
Figure 1 - Pin Diagram
Standard pin configuration offered in both
8 SOIC and TSSOP packages
Alternative pin configuration available only
for 8 TSSOP package
P278XA-08S
P278XA-08T
1 8
6
4
3
2 7
5
XIN
VSS
FS1
LF
XOUT
VDD
FS0
ModOut
P278XB-08T
1 8
6
4
3
2 7
5
FS0
VDD
XIN
XOUT
ModOut
VSS
LF
FS1
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
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®
Figure 2 - P278XX Block Diagram
P278XX Block Diagram
Output
Divider
XIN
VSS
ModOUT
XOUT
Crystal
Oscillator
Modulation
Phase
Detector
Frequency
Divider
Feedback
Divider
VCO
PLL
FS0 FS1 VDD
LF
PIN DESCRIPTION (P278XA)
PIN # Name Type Description
1 XIN/CLKIN
I Connect to crystal or clock input.
2 XOUT I Crystal output
3 FS1 I Digital logic input used to select input frequency range (see Table 1). 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 % spread can be adjusted accordingly. See Table 2 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 Table 1). This
pin has an internal pull-up resistor.
8 VDD P Connect to +3.3V
Table 1 - Input Frequency Selection
Output Frequency Scaling (MHz) FS1 FS0 Input
(MHz) P2781X P2782X P2784X Modulation Rate
(KHz)
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
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
3 of 3 http://www.pulsecore.com
®
Table 2 - Loop Filter Selection Table VDD 3.3V
NOTE: The BW % value is representative of typical conditions.
BW=+/-0.50% BW=+/-0.75% BW=+/-1.00% BW=+/-1.25%
INPUT
(MHz) FS1
FS0
C1 (pF)
C2 (pF)
R1
(ohms)
C1 (pF) C2 (pF)
R1
(ohms) C1 (pF) C2 (pF)
R1
(ohms)
C1 (pF) C2 (pF)
R1
(ohms)
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 1 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
*Please contact factory for loop filter values not listed in the above table
(info@pulsecore.com; or Ext. 17 or 25)
C2 C1
R1
PIN 4 LF
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
4 of 4 http://www.pulsecore.com
®
SPREAD SPECTRUM SELECTION
The P278xA performs Zero Cycle Slip when sets at low % 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).
Example: The P2781A is designed for PC peripheral, networking, notebook PC, and LCD monitor
applications. It is optimized for operation between 3 to 78 MHz range. The P2781A’s spread % selection is
determined by the external LF value specified in Table 2. Table 1 specifies the input frequency range. The
external LF allows the user to fine tuning the spread % to optimize the EMI reduction benefits of the spread
spectrum.
Figure 3 - P278xA Application Schematic
+3.3V
1 8
6
4
3
2 7
5
CLKIN
XOUT
FS1
LF
VDD
ModOUT
FS0
VSS
16MHz
P2781A
Modulated 16MHz with
+/-0.5% BW to target
chip
0.1uF
R1
C2 C1 0 Ohm
560pF
820 Ohm
100,000 pF
Note: Both logic input pins FS1 and FS0 have to be connected to either VDD or VSS by a low impedance
connection such as a printed circuit board trace or zero ohms resistor. Do not leave them floating.
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
5 of 5 http://www.pulsecore.com
®
EMC SOFTWARE SIMULATION
By using PulseCore Semiconductor, Inc.’s proprietary EMC simulation software – EMI-lator®, radiated
system level EMI analysis can be made easier to allow a quantitative assessment on PulseCore’s EMI
reduction products. The simulation engine of this EMC software has already been characterized to correlate
with the electrical characteristics of PulseCore EMI reduction IC’s. Figure 4 below is an example of the
simulation result. Please visit our web site at www.pulsecore.com for information on how to obtain a free
copy and demonstration of EMI-lator®.
Figure 4 - Simulation Result from EMI-lator®
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
6 of 6 http://www.pulsecore.com
®
ABSOLUTE MAXIMUM RATINGS P278XX
Symbol Parameter Rating Unit
VDD, VIN
Voltage on any pin with respect to GND -0.5 to +7.0 V
TSTG
Storage Temperature -65 to +125 ºC
TA
Operating Temperature 0 to +70 ºC
DC ELECTRICAL CHARACTERISTICS P2781X at VDD=3.3V and Temp = +25oC
Symbol Parameter
Min Typ Max Unit
VIL Input Low Voltage GND – 0.3 - 0.8 V
VIH Input High Voltage 2.0 - VDD + 0.3 V
IIL Input Low Current (internal input pull-up
resistor on FS0 and FS1) - 60 - µA
IIH Input High Current (internal input pull-up
resistor on FS0 and FS1) - 0 - µA
IXOL
XOUT Output Low Current - 10 - mA
IXOH
XOUT Output High Current - 10 - mA
VOL Output Low Voltage (VDD = 3.3V, IOL = 20 mA) - - 0.4 V
VOH Output High Voltage (VDD = 3.3V, IOH = 20
mA) 2.5 - - V
IDD Static Supply Current - 3 - mA
ICC Typical Dynamic Supply Current
(25pF scope probe loading) 5.2
@ 3 MHz 21.2
@ 82 MHz mA
VDD Operating Voltage 3.0 3.3 3.6 V
tON
Power Up Time (CLOOP=0.1µF, at 16MHz,
first locked clock cycle after power up) - 7 - mS
ZOUT Clock Output Impedance (at 16MHz) - 28 - Ω
AC ELECTRICAL CHARACTERISTICS at VDD=3.3V and Temp = +25oC
Symbol Parameter Min Typ Max Unit
fIN Input Frequency: P278XX 3 78 MHz
fOUT Output Frequency: P2781X
P2782X
P2784X[AHZ1]
3
6
12
78
156
312
MHz
tLH
P278XX Output Rise Time (measured at 0.8V to 2.0V,
25pF scope probe loading) 1 ns
tHL
P278XX Output Fall Time (measured at 2.0V to 0.8V,
25pF scope probe loading) 1 ns
tJC
P2781X Jitter (cycle to cycle, +/-6sigma, 1000 sweeps,
+/-0.5% spread, I/O Frequency = 16 MHz) +/-
250 ps
tD
P2781X Output Duty Cycle Deviation (error from 50%
duty cycle, 25pF scope probe loading) +/-1
@ 3 MHz +/-2
@ 82 MHz
%
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
7 of 7 http://www.pulsecore.com
®
∆F
P278XX Frequency deviation tolerance from BW%
stated in Table2 -20 0 +20 %
Figure 5 - Mechanical Package Outline (8 Pin SOIC)
D
A1
eB
A
A2
X278XA
LOT NUMBER
YYWW H
a
C
L
E
Figure 6 - Mechanical Package Outline (8 Pin TSSOP)
D
A1
eB
A
A2
H
a
C
L
E
X
278xx
Lot #
YYWW
INCHES MILLIMETERS
SYMBOL
MIN NOR
MAX MIN NOR
MAX
A 0.057
0.064
0.071
1.45
1.63 1.80
A1 0.004
0.007
0.010
0.10
0.18 0.25
A2 0.053
0.061
0.069
1.35
1.55 1.75
B 0.012
0.016
0.020
0.51
0.41 0.31
C 0.004
0.006
0.001
0.10
0.15 0.25
D 0.186
0.194
0.202
4.72
4.92 5.12
E 0.148
0.156
0.164
3.75
3.95 4.15
e 0.050 BSC 1.27 BSC
H 0.224
0.236
0.248
5.70 6.00 6.30
L 0.012
0.020
0.028
0.30 0.50 0.70
a 0° 5° 8° 0° 5° 8°
Note: Controlling dimensions are millimeters.
SOIC - 0.074 grams unit weight
INCHES MILLIMETERS
SYMBOL
MIN NOR
MAX MIN NOR
MAX
A - - 0.047
- - 1.10
A1 0.002
- 0.006
0.05
- 0.15
A2 0.031
0.039
0.041
0.80
1.00 1.05
B 0.007
- 0.012
0.19
- 0.30
C 0.004
- 0.008
0.09
- 0.20
D 0.114
0.118
0.122
2.90
3.00 3.10
E 0.169
0.173
0.177
4.30
4.40 4.50
e 0.026 BSC 0.65 BSC
H 0.244
0.252
0.260
6.20 6.40 6.60
L 0.018
0.024
0.030
0.45 0.60 0.75
a 0° - 8° 0° - 8°
Note: Controlling dimensions are millimeters.
TSSOP - 0.034 grams unit weight
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
8 of 8 http://www.pulsecore.com
®
Ordering Information:
X 278XX- 08 XX
Available Ordering Numbers:
Ordering Number Marking Package Type QTY / Reel Temperature
X278XA-08ST X278XA 8 PIN SOIC, TUBE See flow
X278XA-08SR X278XA 8 PIN SOIC, TAPE & REEL 2,500 See flow
X278XA-08TT X278XA 8 PIN TSSOP, TUBE See flow
X278XA-08TR X278XA 8 PIN TSSOP, TAPE & REEL
2,500 See flow
X278XB-08TT X278XB 8 PIN TSSOP, TUBE See flow
X278XB-08TR X278XB 8 PIN TSSOP, TAPE & REEL
2,500 See flow
Flow
P=Commercial Temperature Range (0°C to 70°C)
I =Industrial Temperature Range (-25°C to 85°C)
A = Automotive Temperature Range (-40°C to 125°C)
Device Number
Device Pin Count
Package
ST=SOIC in Tube
SR=SOIC in Tape and Reel
TT=TSSOP in Tube
TR=TSSOP in Tape and Reel
Alliance Semiconductor
Final Specification
P2781/82/84
Oct, 2002 PulseCore – A Division of Alliance Semiconductor
Revision F 3160 De La Cruz Blvd., Suite 200 • Santa Clara • CA • 95054
Tel (408) 748-6988 • Fax (408) 748-0009
9 of 9 http://www.pulsecore.com
®
Document Information History
REVISION DCR # ISSUE DATE DESCRIPTION OF CHANGE
E 221 Sep. 13, 2002 -Added P2781/82/84B as the alternative 8 TSSOP pinout
-Part numbering information
-AC characteristics to include output frequency for P2782/84
"Licensed under U.S. Patent Nos. 5,488,627 and 5,631,920"
Preliminary data sheet. Specifications subject to change without notice.
