ICS9148-18

Integrated Circuit Systems, Inc. ICS9148-18 Pentium/ProTM System Clock Chip General Description The ICS9148-18 is a Clock Synthesizer chip for Pentium and PentiumPro CPU based Desktop/Notebook systems that will provide all necessary clock timing. Features include two CPU and six PCI clocks. One reference output is available equal to the crystal frequency. Additionally, the device meets the Pentium power-up stabilization requirement, acheiving stable CPU and PCI clocks 2ms after power-up. PD# pin can enable a low power mode by stopping crystal OSC and PLL stages. Other power management features include, CPU_STOP# which stops CPU (0:1) clocks, and PCI_STOP# which stops PCICLK (0:4) clocks. High drive CPUCLK outputs typically provide greater than 1 V/ns slew rate into 20pF loads. PCICLK outputs typically provide better than 1V/ns slew rate into 30pF loads while maintaining 50±5% duty cycle. The REF clock output typically provides better than 0.5V/ns slew rates. The ICS9148-18 accepts a 14.318MHz reference crystal or clock as its input and runs on a 3.3V core supply. Features • • • • • • • • • Generates system clocks for CPU, PCI, plus 14.314 MHz REF0. Supports single or dual processor systems Skew from CPU (earlier) to PCI clock (rising edges for 100/33.3MHz) 1 to 4ns Separate 2.5V and 3.3V supply pins 2.5V or 3.3V output: CPU 3.3V outputs: PCI, REF No power supply sequence requirements Uses external 14.318MHz crystal, no external load cap required for CL=18pF crystal 28 pin ...