W83194BR-645 Datasheet, PDF (3/24 Pages) Winbond – CLOCK GENERATOR FOR SIS 645/650 CHIPSET

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
-1-
Revision 2.1