ICST AV9154A-43CN16, AV9154A-42CS16, AV9154A-42CN16, AV9154A-27CS16, AV9154A-27CN16 Datasheet
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Integrated
Circuit
Systems, Inc.
General Description
Pentium is a trademark of Intel Corporation
Low-Cost 16-Pin Frequency Generator
AV9154A
.
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 dri ve applications. Howev er,
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-fr ee
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 and AV9154A-43 devices offer f eatures 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
• 0.8µm CMOS technology
Applications
Computer motherboards: The AV9154A-ST replaces crystals
and oscillators, saving board space, component cost, part
count and inventor y costs. It produces a switchable CPU clock
and up to four fixed clocks to dri ve 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
2
AV9154A
Pin Configuration
16-Pin PDIP or SOIC
AV9154A-27
16-Pin PDIP or SOIC
AV9154A-42
16-Pin PDIP or SOIC
AV9154A-43
Description of new pin:
SLOWCLK# forces 2XCPUCLK
output to ramp smoothly to
8MHz and CPUCLK output to 4
MHz when pulled low.
Description of new pis:
SLOWCLK# for ces 2XCPUCLK
output to ramp smoothly to
8MHz when pulled low.
STOPCLK# provides gilitchfree stop of the 2XCPUCLK
output when pulled low. When
raised back high, the
2XCPUCLK output clock
resumes full speed operation
(no clock frequency ramp up
since the internal VCO is not
stopped).
16-Pin PDIP or SOIC
9154-04
16-Pin PDIP or SOIC
9154-26
16-Pin PDIP or SOIC
9154-10
3
AV9154A
Stop Clock Feature
The ICS9154A-43 incorporates a unique stop clock
feature compatible with static log ic processors. When
the stop clock pin goes low, the 2XCPUCLK will go
low after the next occurring falling edge. When
STOPCLK again goes high, 2XCPUCLK resumes on
the next rising edge of the internal clock. This feature
enables fast, glitch-free starts and stops of the
2XCPUCLK and is guaranteed that the CPU does not
receive any short period clocks.
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