ICD2027
PC Motherboard Clock Generator
Features
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Block Diagram
Six clock outputs handle all clocking
requirements for personal computer
motherboards
Phase locked loop oscillator input
derived from single 14.31818 MHz
crystal
Frequency range: 760 kHz to 100 MHz
with 50% duty cycle
Two power down modes hardware
pin and software programmable
Concurrent and low skew
1 and
2,
CPUCLK outputs
Ideally suited for desktop PC, laptop,
and notebook applications
Battery input maintains 32.768 kHz
clock during power down
Three state oscillator control disables
outputs for test purposes
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Functional Description
Sophisticated internal loop filter
requires no external components
5V operation
Low power, high speed CMOS
technology
Available in 20 pin SOIC package
configuration
single monolithic device, thus lowering
manufacturing costs and significantly
reducing the printed circuit board space
required.
The ICD2027 PC Motherboard Clock
Generator offers two oscillators, two
phase locked loops, and six different
outputs in a single package. Four of the
outputs are of a fixed value, while the
other two may be changed on the fly" to
any one of 16 preset frequency values
between 760 kHz and 100 MHz. The
ICD2027 is ideally suited for use in
laptop/notebook designs due to its dual
power down modes. The ICD2027 also
requires
no
support
from
the
motherboard chip set and outputs all six
frequencies concurrently.
A modern personal computer mother
board often requires as many as seven
different crystal can oscillators per
printed circuit board. A new family of
frequency synthesis parts from Cypress/IC
Designs replaces the large number of
oscillators required to build such multi
function motherboards. These parts syn
thesize all the required frequencies in a
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BATT
32XIN
32XOUT
OSCILLATOR
32.768 kHz
14.318 MHz
XTALIN
OSCILLATOR
XTALOUT
(INPUT FROM 14.31818 MHz
CRYSTAL)
PLL #1
48 MHz
2
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2
24.0 MHz
1.843 MHz
CPUCLK/2
CPUCLK
PHASE
DETECTOR
S0
S1
S2
S3
PWRDWN
ROM
CHARGE
VCO
PUMP
Internal Loop Filter
2m
Phase Locked Loop Oscillator #2
POWER
CIRCUITRY
GND V
DD
AV
DD
OE
ICD2027 1
Cypress Semiconductor Corporation
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3901 North First Street
1
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San Jose
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CA 95134
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408-943-2600
June 1994 - Revised March 1995
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