ETC
ETC


I2779A

Low-Cost Notebook EMI Reduction IC


I2779A Datasheet PDF
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Production
February 2003
® P2779A
Low-Cost Notebook EMI Reduction IC
Features
• Provides up to 15 dB of EMI suppression
• FCC approved method of EMI attenuation
• Generates a 1X low EMI spread spectrum clock of
the input frequency
• Operates between 20MHz and 38MHz input fre-
quency range
• External loop filter for spread percentage adjust-
ment
• Spreading ranges from ±0.25% to ±2.5%
• Ultra low cycle-to-cycle jitter
• Zero-cycle slip at small deviations
• 3.3 V operating voltage range
• 10 mA output drives
• TTL or CMOS compatible outputs
• Low power CMOS design
• Available in 8-pin SOIC and TSSOP
• Available for industrial temperature operating
range (-40º C to 85º C)
Block Diagram
PD LF VDD
XIN
XOUT
Crystal
oscillator
REF
Frequency
divider
Feedback
divider
Modulation
Phase
detector
Loop
filter
PLL
VCO
Output
divider
ModOUT
Product Description
The P2779A is a versatile spread spectrum frequency
modulator designed specifically for mobile and digital
camera and other digital video and imaging
applications. The P2779A reduces electromagnetic
interference (EMI) at the clock source, which provides
system-wide reduction of EMI of all clock dependent
signals. The P2779A allows significant system cost
savings by reducing the number of circuit board layers
and shielding that are traditionally required to pass EMI
regulations.
The P2779A uses the most efficient and optimized
modulation profile approved by the FCC.
The P2779A 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
VSS
produced by oscillators and most frequency generators.
Lowering EMI by increasing a signal’s bandwidth is
called spread spectrum clock generation.
Applications
The P2779A is targeted toward mobile 3D graphics chip
set applications
Pin Diagram
XIN/CLKIN 1
XOUT 2
PD 3
LF 4
8 VDD
7 REF
6 ModOUT
5 VSS
Alliance Semiconductor
2575 Augustine Drive • Santa Clara, CA 95054 • Tel: 408.855.4900 • Fax: 408.855.4999 • www.alsc.com
Notice: The information in this document is subject to change without notice.


I2779A Datasheet PDF
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P2779A
®
Pin Description
Pin #
1
2
3
Name
XIN/CLKIN
XOUT
PD
Type
I
I
I
4 LF I
5 VSS P
6 ModOUT O
7 REF O
8 VDD P
1. Connect to VDD if not used.
Description
Connect to crystal or clock input.
Crystal output.
Power-down control pin. Pull low to enable power-down mode. This pin has an
internal pull-up resistor.1
External loop filter for the PLL. By changing the value of the CRC circuit, the
percentage spread can be adjusted accordingly. (See Loop Filter Selection
Table for detail value.)
Ground connection. Connect to system ground.
Spread Spectrum clock output.
Provides a reference clock output of the input frequency.
Connect to +3.3 V.
Loop Filter Selection Table VDD 3.3 V
R1
Pin 4 LF
C2 C1
BW = ± 0.50%
BW = ± 0.75%
BW = ± 1.00%
BW = ± 1.25%
Input
(MHz)
FS1
FS0
C1
C2
R1 C1 C2
R1 C1 C2
R1 C1 C2
R1
(pF) (pF) (ohms) (pF) (pF) (ohms) (pF) (pF) (ohms) (pF) (pF) (ohms)
20
21 - 22
23 - 24
25 - 26
27 - 28
29 - 30
31 - 32
33 - 34
35 - 36
37 - 38
1
1
1
1
1
1
1
1
1
1
0 270 100,000 330 270 100,000 560 270 100,000 750 560 100,000 910
0 270 100,000 390 270 100,000 620 270 100,000 866(1%) 560 100,000 1,100
0 270 100,000 510 270 100,000 750 270 10,000 1,000 680 6,800 1,200
0 270 100,000 560 270 100,000 820 270 12,000 1,200 470 4,700 1,200
0 270 100,000 620 270 100,000 1,000 270 6,800 1,200 330 3,300 1,200
0 270 100,000 750 270 100,000 1,100 270 3,900 1,200 330 3,300 1,500
0 270 100,000 820 270 100,000 1,200 270 12,000 2,200 680 6,800 2,200
0 270 100,000 910 270 100,000 1,300 270 10,000 2,200 390 3,900 2,200
0 270 100,000 1,000 270 100,000 1,500 270 5,600 2,200 270 2,700 2,200
0 270 100,000 1,200 270 100,000 1,600 270 3,300 2,200 270 2,700 2,700
Plese contact factory for loop filter values if desired spread settings are not listed.
February 2003
Low-Cost Notebook EMI Reduction IC
Notice: The information in this document is subject to change without notice.
2 of 6


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P2779A
®
Spread Spectrum Selection
The P2779A performs zero cycle slip when set at low percentage spreading. This prevents any 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 that the center
frequency is the frequency of the external reference input on CLKIN, pin 1.)
The P2779A is designed for PC peripheral, networking, notebook PC, and LCD monitor applications. It is optimized
for operation from 20 MHz to 38 MHz. The P2779A’s spread percentage selection is determined by the external LF
value specified in the Loop Filter Selection Table. The external LF allows the user to fine tune the spread
percentage to optimize the EMI reduction benefits of the spread spectrum.
Application Schematic
27 MHz
C2
1 CLKIN
VDD 8
2 XOUT
VDD
3 PD
REF 7
ModOUT 6
R1
C1
4 LF
P2779A
VSS 5
0.1 uF
+3.3 V
Modulated 27 MHz
PD selection: Power dissipation can be reduced by completely turning off the IC.
February 2003
Low-Cost Notebook EMI Reduction IC
Notice: The information in this document is subject to change without notice.
3 of 6


I2779A Datasheet PDF
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P2779A
®
Absolute Maximum Ratings
Symbol
VDD, VIN
TSTG
TA
Parameter
Voltage on any pin with respect to GND
Storage temperature
Operating temperature
DC Electrical Characteristics
Symbol
Parameter
VIL
VIH
IIL
IIH
IXOL
IXOH
VOL
VOH
IDD
ICC
VDD
tON
ZOUT
Input low voltage
Input high voltage
Input low current (internal input pull-up resistor)
Input high current (internal input pull-up resistor on
DIV2 and SR0)
XOUT output low current (at 0.4 V, VDD = 3.3 V)
XOUT output high current (at 2.5 V, VDD = 3.3 V)
Output low voltage (VDD = 3.3 V, IOL = 20 mA)
Output high voltage (VDD = 3.3 V, IOH = 20 mA)
Static supply current
Dynamic supply current (3.3 V, 25 pF loading,
32 MHz)
Operating voltage
Power-up time (first locked cycle after power up)
Clock output impedance
AC Electrical Characteristics
Symbol
Parameter
fIN
fOUT
tLH1
tHL1
tJC
tD
Input frequency
Output frequency
Output rise time (measured at 0.8 V to 2.0 V)
Output fall time (measured at 2.0 V to 0.8 V)
Jitter (cycle to cycle)
Output duty cycle
1. tLH and tHL are measured into a capacitive load of 15 pF.
Rating
-0.5 to +7.0
-65 to +125
-40 to +85
Min
GND - 0.3
2.0
2.5
3.0
Typ
60
0
10
10
3
12
3.3
7
28
Min Typ
20 –
20 –
–1
–1
– ± 175
45 50
Units
V
°C
°C
Max
0.8
VDD + 0.3
Units
V
V
µA
µA
– mA
– mA
0.4 V
–V
– mA
mA
3.6 V
– mS
Max Units
38 MHz
38 MHz
– ns
– ns
– ps
55 %
February 2003
Low-Cost Notebook EMI Reduction IC
Notice: The information in this document is subject to change without notice.
4 of 6


I2779A Datasheet PDF
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P2779A
®
Mechanical Package Outline (8-Pin SOIC)
P2779A
LOT NUMBER
YYWW
H
D
Be
A2 A
A1
C
L
E
a
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 0.31 0.41 0.51
C 0.004 0.006 0.01 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
Mechanical Package Outline (8-Pin TSSOP)
H
D
Be
A2 A
A1
C
L
E
a
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
February 2003
Low-Cost Notebook EMI Reduction IC
Notice: The information in this document is subject to change without notice.
5 of 6


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P2779A
®
Ordering Information
X 2779A- 08 XX X
F = Pb free
Package: ST = SOIC in Tube
SR = SOIC in Tape and Reel
TT = TSSOP in Tube
TR = TSSOP in Tape and Reel
Device pin count
Device Number
Flow: P = Commercial temperature range (0° C to 70° C)
I = Industrial temperature range (-25° C to 85° C)
Available Ordering Numbers
Order Number Marking
Input
Frequency
(MHz)
Package type
Quantity/reel Temperature
P2779A-08ST
P2779A-08SR
P2779A-08TT
P2779A-08TR
P2779A
P2779A
P2779A
P2779A
20 - 38
20 - 38
20 - 38
20 - 38
8-pin SOIC, tube
8-pin SOIC, tape & reel
8-pin TSSOP, tube
8-pin TSSOP, tape & reel
2,500
2,500
0° C to 70° C
0° C to 70° C
0° C to 70° C
0° C to 70° C
Products are available for industrial temperature range operation. Please contact the factory for more information.
© Copyright 2003 Alliance Semiconductor Corporation. All rights reserved. Our three-point logo, our name and Intelliwatt are trademarks or registered trademarks of Alliance. All other brand and product
names may be the trademarks of their respective companies. Alliance reserves the right to make changes to this document and its products at any time without notice. Alliance assumes no responsibility
for any errors that may appear in this document. The data contained herein represents Alliance's best data and/or estimates at the time of issuance. Alliance reserves the right to change or correct this
data at any time, without notice. If the product described herein is under development, significant changes to these specifications are possible. The information in this product data sheet is intended to
be general descriptive information for potential customers and users, and is not intended to operate as, or provide, any guarantee or warrantee to any user or customer. Alliance does not assume any
responsibility or liability arising out of the application or use of any product described herein, and disclaims any express or implied warranties related to the sale and/or use of Alliance products including
liability or warranties related to fitness for a particular purpose, merchantability, or infringement of any intellectual property rights, except as express agreed to in Alliance's Terms and Conditions of Sale
(which are available from Alliance). All sales of Alliance products are made exclusively according to Alliance's Terms and Conditions of Sale. The purchase of products from Alliance does not convey a
license under any patent rights, copyrights, mask works rights, trademarks, or any other intellectual property rights of Alliance or third parties. Alliance does not authorize its products for use as critical
components in life-supporting systems where a malfunction or failure may reasonably be expected to result in significant injury to the user, and the inclusion of Alliance products in such life-supporting
systems implies that the manufacturer assumes all risk of such use and agrees to indemnify Alliance against all claims arising from such use.
February 2003
Low-Cost Notebook EMI Reduction IC
6 of 6
Notice: The information in this document is subject to change without notice.




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