Integrated

Circuit

Systems, Inc.

General Description

Features

ICS9131

Block Diagram

32 KhZ Motherboard Frequency Generator

9131 Rev B 052897P

The ICS9131 offers a tiny footprint solution for generating

a selectable CPU clock from a 32.768 kHz crystal. The device

allows a variety of microprocessors to be clocked by changing

the state of address lines FS0, FS1, and FS2. The ICS9131 is

the ideal solution for replacing high speed oscillators and for

reducing clock speeds to save power in computers. The

device provides smooth, glitch-free frequency transitions so

that the CPU can continue to operate during slow down or

speed up. The rate of frequency change makes the ICS9131

compatible with all 386DX, 386SX, 486DX, 486DXZ, 486SX

and Pentium™ microprocessors.

The ICS9131 is driven from a single 32.768 kHz crystal. The

only external components required are the crystal and a 10M

ohm resistor. The device generates the 14.318 MHz system

clock, eliminating the need for a 14.318 MHz crystal. High-

Performance applications may require high speed clock

termination components.

•

Single 32.768 kHz crystal generates system clock and

selectable CPU clock

•

Generates CPU clocks from 8 MHz to 100 MHz.

•

Operates from 3.3V or 5.0V supply

•

Operates up to 66 MHz at 3.3V

•

Separate VDD for 32 kHz clock enables it to run from

battery

•

STOPCLK feature allows for a glitch-free turn-on and

Pen-turn-off of the CPU clock to static processors

•

Output enable tristates outputs

•

16-pin PDIP or SOIC package

•

Frequency selects allow for a smooth transition of

the CPUCLK

VDD32 Supply

The ICS9131 has a separate power supply for the 32.768 kHz

oscillator circuitry. This allows the 32 kHz clock to run from

a battery or other source while the main power to the chip is

disconnected. The VDD32 supply is guaranteed to operate

down to +2.0V, with the clock consuming less than 10µA at

+3.3V and the main VDD at 0V.

The frequencies and power-down options in the ICS9131 are

mask programmable. Customer specific masks can be made

and prototypes delivered within 6-8 weeks from receipt of

order. ICS also offers standard versions, such as those de-

scribed in this data sheet.

Pentium is a trademark of Intel.

Pin Configuration

16-Pin DIP or SOIC