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.A 14.318 MHz XTAL oscillator
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)
STP0# STP1# DOZE# FS(0:1) (MHz)
CPU2,
ECPU
BUS(0:5) REF(0:3)
(MHz)
(MHz)
1
1
1
1
1
1
1
1
0
0
0
0
X
X
X
X
X
X
X
X
1
0
0*
1
1
1
1
1
0
0
0
0
1
1
0*
0
00
01
10
11
00
01
10
11
--
XX
XX
XX
66.6*
60*
50
40
33.3
30
25
22.5
Stop
Stop
Low
66.6*
60*
50
40
33.3
30
25
22.5
Run
Stop
Low
33.3
33.3
33.3
33.3
16.7
16.7
16.7
16.7
Run
Stop
Low
14.318
14.318
14.318
14.318
14.318
14.318
14.318
14.318
14.318
14.318
14.318
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.
COMPAQ is a trademark of Compaq Computers.
Pentium is a trademark of Intel Corporation.
9159-06 Rev C 091897
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.
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
