Integrated
Circuit
Systems, Inc.
ICS9169C-27
Frequency Generator for Pentium Based Systems
General Description
Features
Twelve selectable CPU clocks operate up to 83.3MHz
Maximum CPU jitter of ± 200ps
Six BUS clocks support sync or async bus operation
250ps skew window for CPU outputs, 500ps skew
window for BUS outputs
CPU clocks BUS clocks skew 1-4ns (CPU early)
Integrated buffer outputs drive up to 30pF loads
3.0V - 3.7V supply range, CPU(1:6) outputs 2.5V(2.375-
2.62V)VDD option
32-pin SOIC/SOJ package
The ICS9169C-27 is a low-cost frequency generator
designed specifically for Pentium based chip set systems.
The integrated buffer minimizes skew and provides all the
clocks required. 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.
Twelve CPU clock outputs provide sufficient clocks for the
CPU, chip set, memory and up to two DIMM connectors (with
four clocks to each DIMM). Either synchronous(CPU/2) or
asynchronous (32 MHz) PCI bus operation can be selected
by latching data on the BSEL input
Logic inputs latched at Power-On for frequency selection
saving pins as Input/Output
48 MHz clock for USB support and 24 MHz clock for FD.
Block Diagram
Pin Configuration
32-Pin SOIC/SOJ
Functionality
3.3V±10%, 0-70°C
Crystal (X1, X2) = 14.31818 MHz
ADDRESS
SELECT
CPU(1:12)
(MHz)
BUS (1:6)MHz
48MHz 24MHz
REF
FS2 FS1 FS0
BSEL=1 BSEL=0
VDD Groups:
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
50
60
25
30
32
32
48
48
24
24
REF
REF
REF
REF
REF
REF
REF
VDD = X1, X2, REF/BSEL
VDDC1 = CPU1-6
VDDC2 = CPU7-12 & PLL Core
VDDB = BUS1-6
VDDF = 48/24 MHz
66.6
REF/2
55
33.3
REF/4
27.5
37.5
41.7
32
48
24
REF/3
32
REF/2
48
REF/4
24
Latched Inputs:
L1 = BSEL
L2 = FS0
L3 = FS1
L4 = FS2
75
32
48
24
83.3
Tristate
32
48
24
Tristate Tristate Tristate Tristate Tristate
Pentium is a trademark on Intel Corporation.
9169C-27 Rev C 04/16/98
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.
ICSI [ INTEGRATED CIRCUIT SOLUTION INC ]
