Integrated

Circuit

Systems, Inc.

General Description

Features

ICS9248- 81

Block Diagram

Pentium is a trademark of Intel Corporation

I

Frequency Generator & Integrated Buffers

9248-81 Rev E 10/12/99

Pin Configuration

•

Generates the following system clocks:

- 3 CPU(2.5V/3.3V) up to 133.3MHz.

- 6 PCI(3.3V) (including 1 free-running)

- 13 SDRAMs(3.3V) up to 133.3MHz.

- 3 REF (3.3V) @ 14.318MHz

- 1 clock @ 24/14.3 MHz selectable output for SIO

- 1 Fixed clock at 48MHz (3.3V)

- 1 IOAPIC @ 2.5V / 3.3V

•

Skew characteristics:

- CPU – CPU<175ps

- SDRAM – SDRAM < 250ps

- CPU–SDRAM < 500ps

- CPU(early) – PCI : 1-4ns (typ. 3ns)

- PCI – PCI <500ps

•

Supports Spread Spectrum modulation ±0.25 & ±0.5%

center spread

•

Select, Spread Spectrum.

•

Efficient Power management scheme through PCI,

SDRAM, CPU STOP CLOCKS and PD#.

•

Uses external 14.318MHz crystal

•

48 pin 300mil SSOP.

48-Pin SSOP

Power Groups

VDDREF=REF[2:0],X1,X2

VDDPCI=PCICLK_F,PCICLK[4:0]

VDDSD/C = SDRAM [11:0], supply for PLL core, 24 MHz, 48MHz

VDD/CPU=CPUCLK[3:1]

VDDLAPIC=IOAPIC

GNDFIX = Ground for fixed clock PLL and output buffers

* Internal Pull-up Resistor of

120K to 3.3V on indicated inputs

The ICS9248-81 is the single chip clock solution for Desktop/

Notebook designs using the SIS style chipset. It provides all

necessary clock signals for such a system.

Spread spectrum typically reduces system EMI by 8dB to

10dB. This simplifies EMI qualification without resorting to

board design iterations or costly shielding. The ICS9248-81

employs a proprietary closed loop design, which tightly

controls the percentage of spreading over process and

temperature variations.

stop clock programming and frequency selection. The SD_SEL

latched input allows the SDRAM frequency to follow the

CPUCLK frequency(SD_SEL=1) or other clock frequencies

(SD_SEL=0)

ICS reserves the right to make changes in the device data identified in

this publication without further notice. ICS advises its customers to

obtain the latest version of all device data to verify that any

information being relied upon by the customer is current and accurate.