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W83194BR-645

CLOCK GENERATOR FOR SIS 645/650 CHIPSET

Winbond 

W83194BR-645

1. GENERAL DESCRIPTION

The W83194BR-645 is a Clock Synthesizer for SiS645/650 chipset. W83194BR-645 provides all

clocks required for high-speed Intel Pentium 4, and also provides 32 different frequencies of CPU

clocks frequency setting. All clocks are externally selectable with smooth transitions. The W83194BR-

645 makes SDRAM in synchronous or asynchronous frequency with CPU clocks.

The W83194BR-645 provides step-less frequency programming by controlling the VCO freq. and the

programmable AGP, PCI clock output divisor ratio. A watchdog timer is quipped and when time out,

register9 bit5 will be set to 1 for warning. Spread spectrum built in at ±0.5% or ±0.25% to reduce EMI.

Programmable stopping individual clock outputs and frequency selection through I2C interface

The W83194BR-645 accepts a 14.318 MHz reference crystal as its input and runs on a 3.3V supply.

High drive PCI CLOCK outputs typically provide greater than 1V /nS slew rate into 30 pF loads. The

fixed frequency outputs as REF, 24 MHz, and 48 MHz provide better than 0.5V /nS slew rate.

2. FEATURES

• Supports Intel Pentium 4 CPU with I2C.

• 2 pairs of differential CPU clocks

• 2 ZCLK for SiS 645/650 chipset

• 2 AGP clocks

• 1 SDRAM output clock for chipset

• 8 PCI synchronous clocks

• 1 24/48 MHz, 1 48 MHz

• 3 REF clocks

• Skew --- CPU to SDRAM < 1 nS, PCI to PCI < 500 pS, AGP to AGP < 175 pS

• Smooth frequency switch with selections from 66 to 200 MHz

• I2C 2-Wire serial interface and I2C read back

• Flexible spread spectrum to reduce EMI

• Programmable registers to enable/stop each output and select modes

(Mode as Tri-state or Normal)

• Packaged in 48-pin SSOP

Publication Release Date: April 13, 2005

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Revision 2.1

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