ICST AV9154A-43CN16, AV9154A-42CS16, AV9154A-42CN16, AV9154A-27CS16, AV9154A-27CN16 Datasheet

Integrated
Circuit	AV9154A
Systems, Inc.

Low-Cost 16-Pin Frequency Generator

General Description

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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 phaselocked 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.

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

•0.8 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.

Block Diagram

Pentium is a trademark of Intel Corporation

9154 Rev B 04/17/97

AV9154A

Pin Configuration

16-Pin PDIP or SOIC					16-Pin PDIP or SOIC
		AV9154A-27			AV9154A-42
					Description of new pin:
					SLOWCLK# forces 2XCPUCLK
					output to ramp smoothly to
					8MHz and CPUCLK output to 4
					MHz when pulled low.

16-Pin PDIP or SOIC AV9154A-43

Description of new pis:

SLOWCLK# forces 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				16-Pin PDIP or SOIC
9154-04	9154-10

16-Pin PDIP or SOIC

9154-26

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AV9154A

Stop Clock Feature

The ICS9154A-43 incorporates a unique stop clock feature compatible with static logic 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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