ICS9248-78 Datasheet | Integrated Circuit Systems

Integrated Circuit Systems, Inc. Preliminary Product Preview Frequency Timing Generator for Pentium II Systems General Description The ICS9248-78 is a single chip clock for Intel Pentium II. It provides all necessary clock signals for such a system. Spread spectrum may be enabled through I2C programming. Spread spectrum typically reduces EMI by 8d B to 10 d B. This simplifies EMI qualification without resorting to board design iterations or costly shielding. The ICS9248-78 employs a proprietary closed loop design, which tightly controls the percentage of spreading over process and temperature variations. Features • Generates the following system clocks: - 2 - CPUs @ 2.5V, up to 150MHz. - 1 - IOAPIC @ 2.5V, PCI/2MHz. - 9 SDRAMs (3.3V), up to150MHz. -2 - 3V66 @ 3.3V, 2x PCIMHz. - 8 - PCIs @ 3.3V. - 1 - 48MHz, @ 3.3V fixed. - 2 - REF @ 3.3V, 14.318Hz. - 1 - 24MHz, @ 3.3V fixed. Supports spread spectrum modulation , down spread 0 to -0.5%, ±0.25% center spread. I2C support for power management. Efficient power management scheme through PD#. Uses external 14.138 MHz crystal. • • • • Block Diagram Pin Configuration 48-Pin 300 mil SSOP Power Groups GNDREF, VDDREF = REF, Crystal GND3V66, VDD3V66 = 3V66 GNDPCI, VDDPCI = PCICLKs GNDCOR, VDDCOR = PLLCORE GND48, VDD48 = 48 GNDSDR, VDDSDR = SDRAM GNDLCPU, VDDLCPU = CPUCLK GNDLPCI, VDDLAPIC = IOAPIC 9248-78 Rev A 7/21/99 1. These pins will have 2X drive strength. - 120K ohm pull-up to VDD on indicated...