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Production February 2003
(R)
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 frequency range External loop filter for spread percentage adjustment 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 (-40 C to 85 C)
Block Diagram
PD LF VDD
XIN XOUT
Modulation Crystal oscillator Frequency divider Feedback divider Phase detector Loop filter
PLL
VCO
Output divider
REF
ModOUT
VSS
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
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 XOUT PD LF 1 2 3 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.
P2779A
(R)
Pin Description
Pin # 1 2 3 4 Name XIN/CLKIN XOUT PD LF Type I I I I 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. Description
5 6 7 8
VSS ModOUT REF VDD
P O O P
1. Connect to VDD if not used.
Loop Filter Selection Table VDD 3.3 V
R1 Pin 4 LF C2 C1
BW = 0.50% Input FS1 FS0 (MHz)
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 0 0 0 0 0 0 0 0 0
BW = 0.75% C1
270 270 270 270 270 270 270 270 270 270
BW = 1.00% C1
270 270 270 270 270 270 270 270 270 270
BW = 1.25% C1
560 560 680 470 330 330 680 390 270 270
C1 (pF)
270 270 270 270 270 270 270 270 270 270
C2 (pF)
100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000
R1
330 390 510 560 620 750 820 910 1,000 1,200
(ohms) (pF)
C2 (pF)
100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000 100,000
R1
560 620 750 820 1,000 1,100 1,200 1,300 1,500 1,600
(ohms) (pF)
C2 (pF)
100,000 10,000 12,000 6,800 3,900 12,000 10,000 5,600 3,300
R1
750 1,000 1,200 1,200 1,200 2,200 2,200 2,200 2,200
(ohms) (pF)
C2 (pF)
100,000 100,000 6,800 4,700 3,300 3,300 6,800 3,900 2,700 2,700
R1
(ohms) 910 1,100 1,200 1,200 1,200 1,500 2,200 2,200 2,200 2,700
100,000 866(1%)
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
P2779A
(R)
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
1 CLKIN
VDD
VDD REF ModOUT VSS
P2779A
8 7 6 5
0.1 uF
2 XOUT 3 PD 4 LF
+3.3 V
Modulated 27 MHz
R1 C2 C1
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
P2779A
(R)
Absolute Maximum Ratings
Symbol VDD, VIN TSTG TA Parameter Voltage on any pin with respect to GND Storage temperature Operating temperature Rating -0.5 to +7.0 -65 to +125 -40 to +85 Units V C C
DC Electrical Characteristics
Symbol 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 Parameter Min GND - 0.3 2.0 - - - - - 2.5 -
-
Typ - - 60 0 10 10 - - 3 12 3.3 7 28
Max 0.8 VDD + 0.3 - - - - 0.4 - -
-
Units V V A A mA mA V V mA mA V mS
3.0 - -
3.6 - -
AC Electrical Characteristics
Symbol 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 Parameter Min 20 20 - - - 45 Typ - - 1 1 175 50 Max 38 38 - - - 55 Units MHz MHz ns ns ps %
1. tLH and tHL are measured into a capacitive load of 15 pF.
February 2003
Low-Cost Notebook EMI Reduction IC
Notice: The information in this document is subject to change without notice.
4 of 6
P2779A
(R)
Mechanical Package Outline (8-Pin SOIC)
INCHES
C
MILLIMETERS MAX MIN 1.45 0.10 1.35 0.31 0.10 4.72 3.75 5.70 0.30 0 NOR 1.63 0.18 1.55 0.41 0.15 4.92 3.95 1.27 BSC 6.00 0.50 5 6.30 0.70 8 MAX 1.80 0.25 1.75 0.51 0.25 5.12 4.15
SYMBOL A
L
MIN 0.057 0.004 0.053 0.012 0.004 0.186 0.148 0.224 0.012 0
NOR
0.064 0.071 0.007 0.010 0.061 0.069 0.016 0.020 0.006 0.01 0.194 0.202 0.156 0.164 0.236 0.248 0.020 0.028 5 8
A1 A2 B C D
P2779A
LOT NUMBER YYWW
H E
a D
E e H L
0.050 BSC
A2
A
a
B
e
Note: Controlling dimensions are millimeters.
A1
SOIC - 0.074 grams unit weight
Mechanical Package Outline (8-Pin TSSOP)
INCHES
C
MILLIMETERS MAX 0.047 0.006 0.041 0.012 0.008 0.122 0.177 0.260 0.030 8 MIN - 0.05 0.80 0.19 0.09 2.90 4.30 6.20 0.45 0 NOR - - 1.00 - - 3.00 4.40 0.65 BSC 6.40 0.60 - 6.60 0.75 8 MAX 1.10 0.15 1.05 0.30 0.20 3.10 4.50
SYMBOL
L
MIN - 0.002 0.031 0.007 0.004 0.114 0.169 0.244 0.018 0
NOR - - 0.039 - - 0.118 0.173 0.252 0.024 -
A A1 A2 B C D E e H L a
X P 2779A 278xx
Lot # YYWW
H
E
a D
0.026 BSC
A2
A
B
e
A1
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
P2779A
(R)
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 P2779A-08ST P2779A-08SR P2779A-08TT P2779A-08TR Marking P2779A P2779A P2779A P2779A Input Frequency (MHz) 20 - 38 20 - 38 20 - 38 20 - 38 Package type 8-pin SOIC, tube 8-pin SOIC, tape & reel 8-pin TSSOP, tube 8-pin TSSOP, tape & reel 2,500 2,500 Quantity/reel Temperature 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.
(c) 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
Notice: The information in this document is subject to change without notice.
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