AV9154A Datasheet, PDF (1/10 Pages) Integrated Circuit Systems – Low-Cost 16-Pin Frequency Generator

Integrated
Circuit
Systems, Inc.
AV9154A
Low-Cost 16-Pin Frequency Generator
General Description
._{The AV9154A is a 0.8mm version of the industry leading AV9154.}
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).
Features
• 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
• 0.8µm 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.
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.
Block Diagram
9154 Rev B 04/17/97
Pentium is a trademark of Intel Corporation