ICS9250-22 Datasheet, PDF (2/11 Pages) Integrated Circuit Systems – Frequency Generator for P IV™

ICS9250-22
General Description
The ICS9250-22 is a single chip clock solution.
Spread spectrum typically reduces system EMI by 8dB to 10dB. This simplifies EMI qualification without resorting to
board design iterations or costly shielding. The ICS9250-22 employs a proprietary closed loop design, which tightly
controls the percentage of spreading over process and temperature variations.
Pin Configuration
PIN NUMBER
PIN NAME
TYPE
DESCRIPTION
1, 7, 13, 19, 24, 32,
33, 37, 40, 46, 53
GND
PWR
Ground pins for 3.3V supply
MULTSEL0 and MULTSEL1 inputs are sensed on power-up and
3, 2
REF/MULTSEL (1:0)
IN
then internally latched prior to the pin being used for output on 3V
14.318MHz clocks.
4, 10, 16, 22, 27, 29,
36, 38, 43, 49, 56
VDD
PWR
3.3V power supply
5
X1
X2 Crystal Input 14.318MHz Crystal input
6
X2
X1 Crystal Output 14.318MHz Crystal output
21, 20, 18, 17, 15,
14, 12, 11, 9, 8
PCICLK (9:0)
OUT
PCI clock outputs
23
SEL100/133
IN
CPU Frequency Select. Low=100MHz, High=133MHz
26, 25
FS (1:0)
48MHz
IN
Frequency select pins
OUT
48MHz clock output
28
PD#
IN
Invokes power-down mode. Active Low.
35, 34, 31, 30
3V66 (3:0)
OUT
66MHz reference clocks
This pin establishes the reference current for the CPUCLK pairs.
39
I REF
OUT
This pin takes a fixed precision resistor tied to ground in order to
establish the appropriate current.
51, 48, 45, 42
CPUCLKST (3:0)
OUT
"True" clocks of differential pair CPU outputs. These are switched
current outputs and external resistors are required for voltage bias.
50, 47, 44, 41
CPUCLKSC (3:0)
OUT
"Complementory" clocks of differential pair CPU outputs. These
are switched current outputs and external resistors are required for
voltage bias.
Invokes Spread Spectrum functionality on the Differential host
52
SPREAD#
IN
clocks, MRef/MRef_b clocks, 66MHz clocks, and 33MHz PCI
clocks. Active Low
54
3VMREF_B
OUT
3V reference to memory clock driver
(out of phase with 3Vmref)
55
3VMREF
OUT
3V reference to memory clock driver
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