ICS9159-06 Datasheet, PDF (1/7 Pages) Integrated Circuit Systems – Frequency Generator and Buffer for Pentium Systems

Integrated
Circuit
Systems, Inc.
ICS9159-06
Preliminary Product Preview
Frequency Generator and Buffer for Pentium™ Systems
General Description
The ICS9159-06 is a low cost frequency generator designed
specifically for Pentium systems. The integrated buffer minimizes
skew and provides the early CPU clock required by some
chipsets such as the OPTi VIPER.A14.318 MHz XTALoscillator
provides the reference clock to generate standard Pentium
frequencies. The CPU clock makes gradual frequency transitions
without violating the PLL timing of internal microprocessor
clock multipliers.
Asynchronous 33.3 MHz PCI bus operation is supported,
in-dependent of the CPU operating frequency. Green PC
systems are supported through power-down, doze, and
glitch-free stop clock modes.
Features
• Four CPU clocks operate up to 66 MHz at 3.3V with
glitch-free start and stop plus smooth transitions
• 3-6ns early CPU clock supports OPTi VIPER systems
• Selection of 8 frequencies, tristate, or power-down
• Six BUS clocks support asynchronous PCI bus
operation
• ±250ps skew between synchronous outputs
• Integrated buffer outputs drive up to 30pF loads
• 3.1V -5.5V supply range
• 28-pin 300-mil SOIC package
Applications
• Ideal for green Pentium and 486 PCI systems
Block Diagram
Functionality
3.1 to 5.5V, 0-70° Crystal=14.318 MHz input
CPU(0:1) CPU2, BUS(0:5) REF(0:3)
STP0# STP1# DOZE# FS(0:1) (MHz) ECPU (MHz) (MHz)
1 X 1 00 66.6* 66.6* 33.3 14.318
1 X 1 01 60* 60* 33.3 14.318
1X
1
10
50
50 33.3 14.318
1X
1
11
40
40 33.3 14.318
1 X 0 00 33.3 33.3 16.7 14.318
1X
0
01
30
30 16.7 14.318
1X
0
10
25
25 16.7 14.318
1X
0
11 22.5 22.5 16.7 14.318
01
1
- - Stop Run Run 14.318
00
1 X X Stop Stop Stop 14.318
0 0* 0* X X Low Low Low 14.318
01
0 X X Tristate Tristate Tristate 14.318
* 3.3 volt operation only. ** 000 mode powers-down the
PLL sections and forces the outputs low. To ensure glitch-
free start and stop of the CPU and BUS clocks enter 000
from 001 and exit 000 through 001.
9159-06 Rev C 091897
COMPAQ is a trademark of Compaq Computers.
Pentium is a trademark of Intel Corporation.
PRODUCT PREVIEW documents contain information on new
products in the sampling or preproduction phase of development.
Characteristic data and other specifications are subject to change
without notice.