Integrated

Circuit

Systems, Inc.

General Description

Pentium is a trademark of Intel Corporation

Low-Cost 16-Pin Frequency Generator

AV9154A

Like the AV9154, the AV9154A is a low-cost frequency generator

designed for general purpose PC and disk drive applications. However,

because the AV9154A uses 0.8mm technology and the latest phase-

locked loop architecture, it offers performance advantages that

enable the device to be sold into Pentium™ systems.

The AV9154A guarantees a 45/55 duty cycle over all frequencies. In

addition, a worst case jitter of ±250ps is specified at Pentium

frequencies.

The CPU clock offers the unique feature of smooth, glitch-free

transitions from one frequency to the next, making this the ideal

device to use when slowing the CPU speed. The AV9154A makes a

gradual transition between frequencies so that it obeys the Intel

cycle-to-cycle timing specifications for 486 and Pentium systems.

The AV9154A-42 andAV9154A-43 devices offer features specifically

for green PCs. The AV9154A-42 and -43 have a single pin that,

when pulled low, will smoothly slow the 2XCPU clock to 8 MHz.

This is ideal for dynamic DX microprocessors. The AV9154A-43

not only has the slow clock feature, but also offers a glitch-free stop

clock for static SX microprocessors. The STOPCLK# pin, when

pulled low, enables the 2XCPU clock to go low only after completing

its last full cycle. The clock continues to run internally, and will be

output again on the first full cycle immediately following stop clock

disable.

The simultaneous 2X and 1X CPU clocks offer controlled skew to

within 500ps of each other (-42 only).

ICS has been shipping motherboard frequency generators since

April 1990, and is the leader in the area of multiple output clocks on

a single chip. Consult ICS for all your clock generation needs.

•

Compatible with 386, 486 and Pentium CPUs

•

45/55 Duty cycle

•

Runs up to 66 MHz at 3.3V

•

Single pin can slow clock to 8 MHz (on -42 and -43)

•

Single pin can stop the CPU clock glitch-free (on -43)

•

Very low jitter, ±250ps for Pentium frequencies

•

1X and 2X CPU clocks skew controlled to ±250ps (-42

only)

•

Smooth transitions between all CPU frequencies

•

Slow frequency ramp at power-on avoids CPU lock-up

•

16-pin PDIP or 150-mil skinny SOIC packages

•

0.8

µm CMOS technology

Applications

Computer motherboards: The AV9154A-ST replaces crystals

and oscillators, saving board space, component cost, part

count and inventory costs. It produces a switchable CPU clock

and up to four fixed clocks to drive floppy disk, communications,

super I/O, Bus, and/or keyboard devices. The small package

and 3.3V operation is perfect for handheld computers.

Features

Block Diagram

9154 Rev B 04/17/97