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Details, datasheet, quote on part number:P2784A
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Datasheet text preview:
December 2002
PulseC re
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P2781/82/84
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 Available for industrial and automotive temperature ranges.
Pin Diagram
XIN XOUT FS1 LF 1 2 3 4
P278XA-08S P278XA-08T
8 7 6 5
VDD FS0 ModOut VSS
FS0 VDD XIN XOUT
1 2 3 4
P278XA-08T
8 7 6 5
ModOut VSS LF FS1
Standard pin configuration offered in both 8 SOIC and TSSOP packages.
Alternative pin configuration offered in only 8 TSSOP package
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 toward MFP, xDSL, fax modem, set-top box, USB controller, DSC, and embedded systems.
12/6/02, v. 1.0
Alliance Semiconductor
2575 Augustine Drive, Santa Clara, CA 95054 Tel: 408-855-4900 Fax: 408-855-4999
P. 1 of 7
Copyright © Alliance Semiconductor. All rights reserveG
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Block Diagram
FS0 FS1 LF VDD
PLL XIN XOUT Crystal Oscillator Modulation Frequency Div ider Feedback Div ider
Phase Detector
VC0
Output D ivider
ModOut
VSS
Pin Description (P278XA)
PIN # 1 2 3 4 5 6 7 8 Name X IN /CLKIN XOUT F S1 LF VSS M odOU T F S0 VD D Type I I I I I O I P Connect to crystal or clock input. Crystal output Digital logic input used to select input frequency range (see the Input Frequency Selection Table). This pin has an internal pull-up resistor. 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. Ground Connection. Connect to system ground. Spread Spectrum Clock Output. Digital logic input used to select input frequency range (see the Input Frequency Selection Table). This pin has an internal pull-up resistor. Connect to +3.3 V Description
Input Frequency Selection Table
Output Frequency Scaling (MHz) FS1 0 0 1 1 FS0 0 1 0 1 Input (MHz) 3 to 9 10 to 19 20 to 38 39 to 78 P2781X 3 to 9 10 to 19 20 to 38 39 to 78 P2782X 6 to 18 20 to 38 40 to 76 78 to 156 P2784X 12 to 36 40 to 76 80 to 152 156 to 312 Modulation Rate (KHz) Fin / 128 Fin / 256 Fin / 512 Fin / 1024
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Loop Filter Selection Table VDD 3.3 V
R1 C2 Pin 4 LF C1 Contact Alliance for loop values that are not listed in the table and for component selection values for industrial and automotive temperatures.
BW = ±1.00%1 C1 C2 R1 (pF) (pF) (ohm) 270 100,000 390 270 100,000 560 270 100,000 750 270 10,000 1,000 270 5,600 1,200 270 12,000 2,200 270 5,600 2,200 270 100,000 750 270 100,000 866(1%) 270 10,000 1,000 270 12,000 1,200 270 5,600 1,200 270 3,900 1,200 270 12,000 2,200 270 10,000 2,200 270 5,600 2,200 270 3,300 2,200 270 100,000 750 270 100,000 866 (1%) 270 10,000 1,000 270 12,000 1,200 270 6,800 1,200 270 3,900 1,200 270 12,000 2,200 270 10,000 2,200 270 5,600 2,200 270 3,300 2,200 270 100,000 750 270 100,000 866 (1%) 270 10,000 1,000 270 12,000 1,200 270 6,800 1,200 270 3,900 1,200 270 12,000 2,200 270 8,200 2,200 270 5,600 2,200 270 3,300 2,200 BW = ±1.25%1 C1 C2 R1 (pF) (pF) (ohm) 560 100,000 510 560 100,000 680 560 100,000 910 680 6,800 1,200 330 3,300 1,200 680 6,800 2,200 270 2,700 2,200 560 100,000 910 560 100,000 1,100 680 6,800 1,200 470 4,700 1,200 330 3,300 1,200 330 3,300 1,500 680 6,800 2,200 390 3,900 2,200 270 2,700 2,200 270 2,700 2,700 560 100,000 910 560 100,000 1,100 680 6,800 1,200 470 4,700 1,200 330 3,300 1,200 330 3,300 1,500 680 6,800 2,200 390 3,900 2,200 270 2,700 2,200 270 2,700 2,700 560 100,000 910 560 100,000 1,100 680 6,800 1,200 470 4,700 1,200 330 3,300 1,200 330 3,300 1,500 680 6,800 2,200 390 3,900 2,200 270 2,700 2,200 270 2,700 2,700
Input MHz FS1 FS0 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 1 10 0 1 11 0 1 12 0 1 13 0 1 14 0 1 15 0 1 16 0 1 17 0 1 18 0 1 19 1 0 20 0 21-22 1 0 23-24 1 0 25-26 1 0 27-28 1 0 29-30 1 0 31-32 1 0 33-34 1 0 35-36 1 0 37-38 1 1 39-42 1 1 43-46 1 1 47-50 1 1 51-54 1 1 55-58 1 1 59-62 1 1 63-66 1 1 67-70 1 1 71-74 1 1 75-78 1
BW = ±0.50%1 C1 C2 R1 (pF) (pF) (ohm) 270 330,000 220 270 100,000 270 270 100,000 390 270 100,000 510 270 100,000 620 270 100,000 820 270 100,000 1,000 270 100,000 330 270 100,000 390 270 100,000 510 270 100,000 560 270 100,000 620 270 100,000 750 270 100,000 820 270 100,000 910 270 100,000 1,000 270 100,000 1,200 270 100,000 330 270 100,000 390 270 100,000 510 270 100,000 560 270 100,000 620 270 100,000 750 270 100,000 820 270 100,000 910 270 100,000 1,000 270 100,000 1,200 270 100,000 330 270 100,000 390 270 100,000 510 270 100,000 560 270 100,000 620 270 100,000 750 270 100,000 820 270 100,000 910 270 100,000 1,000 270 100,000 1,200
BW = ±0.75%1 C1 C2 R1 (pF) (pF) (ohm) 270 330,000 300 270 100,000 390 270 100,000 560 270 100,000 750 270 100,000 1,000 270 100,000 1,200 270 100,000 1,500 270 100,000 510 270 100,000 560 270 100,000 750 270 100,000 820 270 100,000 1,000 270 100,000 1,100 270 100,000 1,200 270 100,000 1,300 270 100,000 1,500 270 100,000 1,600 270 100,000 560 270 100,000 620 270 100,000 750 270 100,000 820 270 100,000 1,000 270 100,000 1,100 270 100,000 1,200 270 100,000 1,300 270 100,000 1,500 270 100,000 1,600 270 100,000 560 270 100,000 620 270 100,000 750 270 100,000 820 270 100,000 1,000 270 100,000 1,100 270 100,000 1,200 270 100,000 1,300 270 100,000 1,600 270 100,000 1,800
1 The BW value is representative of typical conditions.
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