ICS9148B-04 Datasheet | Integrated Circuit Systems

Integrated Circuit Systems, Inc. Frequency Generator & Integrated Buffers for PENTIUM/Pro TM General Description The ICS9148B-04 generates all clocks required for high speed RISC or CISC microprocessor systems such as Intel Pentium Pro or Cyrix. Eight different reference frequency multiplying factors are externally selectable with smooth frequency transitions. Features include four CPU, seven PCI and Twelve SDRAM clocks. Two reference outputs are available equal to the crystal frequency. Plus the IOAPIC output powered by VDDL1. One 48 MHz for USB, and one 24 MHz clock for Super IO. Spread Spectrum built in - ±1.5% modulation to reduce the EMI. Serial programming I2C interface allows changing functions, stop clock programing and Frequency selection. Rise time adjustment for VDD at 3.3V or 2.5V CPU. Additionally, the device meets the Pentium power-up stabilization, which requires that CPU and PCI clocks be stable within 2ms after power-up. It is not remended to use I/O dual function pin for the slots (ISA, PCI, CPU, DIMM). The add on card might have a pull up or pull down. • • • • • • • • • • • • • • Features 3.3V outputs: SDRAM, PCI, REF, 48/24MHz 2.5V or 3.3V outputs: CPU, IOAPIC 20 ohm CPU clock output impedance 20 ohm PCI clock output impedance Skew from CPU (earlier) to PCI clock - 1 to 4 ns, center 2.6 ns. No external load cap for CL=18p F crystals ±250 ps CPU, PCI clock skew 400ps (cycle to cycle) CPU jitter Smooth frequency switch, with selections from 50 to 83.3 MHz CPU. I2C interface for programming 2ms power up clock stable time Clock duty cycle 45-55%. 48 pin 300 mil SSOP package 3.3V operation, 5V tolerant input. Pin Configuration Block Diagram 48-Pin SSOP - Internal Pull-up Resistor of 240K to 3.3V on indicated inputs Power Groups VDD1 = REF (0:1), X1, X2 VDD2 = PCICLK_F, PCICLK(0:5) VDD3 = SDRAM (0:11), supply for PLL core, 24MHz, 48MHz VDDL1 = IOAPIC VDDL2 = CPUCLK (0:3) 9148-04 Rev B 01/20/98 Pentium is a trademark of Intel...