9154A Datasheet, PDF (1/11 Pages) Integrated Circuit Systems – Low-Cost 16-Pin Frequency Generator

Integrated
Circuit
Systems, Inc.
9154A
Low-Cost 16-Pin Frequency Generator
General Description
The 9154A is a 0.8mm version of the industry leading 9154.
Like the 9154, the 9154A is a low-cost frequency generator
designed for general purpose PC and disk drive applications.
However, because the 9154A 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 9154A 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
9154A makes a gradual transition between frequencies so
that it obeys the Intel cycle-to-cycle timing specifications for
486 and Pentium systems.
The 9154A-42 and 9154A-43 devices offer features
specifically for green PCs. The 9154A-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 9154A-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 150-mil skinny SOIC packages
• 0.8µm CMOS technology
Applications
Computer motherboards: The 9154A 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
0174E—03/18/08