ICS9159-20 Datasheet, PDF (1/5 Pages) Integrated Circuit Systems – Frequency Generator for SIS551X and SIS6205 Chip Set Systems

Integrated
Circuit
Systems, Inc.
ICS9159-20
Frequency Generator for SIS551X and SIS6205 Chip Set Systems
General Description
The ICS9159-20 is a low-cost frequency generator designed
specifically for SIS551X chip set and SIS6205 VGA control-
ler. The integrated buffer minimizes skew. A 14.31818 MHz
XTAL oscillator provides the reference clock to generate
standard Pentium™ frequencies. The CPU clock makes grad-
ual frequency transitions without violating the PLL timing
of internal microprocessor clock multipliers.
Both synchronous and asynchronous bus designs are sup-
ported. For chip sets that require an early CPU clock, the
buffers are driven by the CPU clock. In this configuration, the
CPU clock becomes the early clock and the output of the
uncommitted buffers become the bus synchronized bus clocks.
Features
• One selectable CPU clocks operate up to 66.66 MHz
• 5 uncommitted buffers
• Maximum CPU jitter of ±200ps
• 7 BUS clocks support sync or async bus operation
• 500ps skew window for all synchronous clock edges
• Integrated buffer outputs drive up to 30pF loads
• 3.1V - 3.5V supply range
• 28-pin 300-mil SOIC package
• Supports chip sets requiring early CPU clocking
Block Diagram
Applications
• Ideal for green Pentium and P6 PCI systems based on the
SIS5596 chip set
Pin Configuration
9159-20 Rev B 040597
28-Pin SOIC
Functionality
3.3V±10%, 0-70°C
Crystal (X1, X2) = 14.318181 MHz
FS1
FS0
REF
CPU
BCLK (MHz)
(MHz) (MHz) BSEL=1 BSEL=0
0
0
Tistate Tristate Tristate Tristate
0
1
14.318
50
1
0
14.318
60
25
33.33
30
33.33
1
1
14.318 66.66 33.33 33.33
All frequencies in MHz, assuming 14.318 MHz input.
Pentium is a trademark of Intel Corporation.
ICS reserves the right to make changes in the device data identified in this publication
without further notice. ICS advises its customers to obtain the latest version of all
device data to verify that any information being relied upon by the customer is current
and accurate.