DATASHEET

SYSTEM PERIPHERAL CLOCK SOURCE

ICS650-21

IDT™ / ICS™ SYSTEM PERIPHERAL CLOCK SOURCE

1

ICS650-21

REV J 051310

Description

The ICS650-21 is a low cost, low-jitter, high-performance

clock synthesizer for system peripheral applications. Using

analog/digital Phase Locked Loop (PLL) techniques, the

device accepts a parallel resonant 25 MHz crystal input to

produce up to eight output clocks. The device provides

clocks for PCI, SCSI, Fast Ethernet, Ethernet, USB, and

AC97. The user can select one of three USB frequencies

and also one of two AC97 audio frequencies. The OE pin

puts all outputs into a high-impedance state for board level

testing. All frequencies are generated with less than one

ppm error, meeting the demands of SCSI and Ethernet

clocking.

Features

• Packaged in 20-pin SSOP (QSOP)

• Pb (lead) free package, RoHS compliant

• Lower jitter version of ICS650-01

• Operating voltage of 3.3 V or 5 V

• Zero ppm synthesis error in all clocks

• Inexpensive 25 MHz crystal or clock input

• Provides Ethernet and Fast Ethernet clocks

• Provides SCSI clocks

• Provides PCI clocks

• Selectable AC97 audio clock

• Selectable USB clock

• OE pin tri-states the outputs for testing

• Selectable frequencies on three clocks

• Duty cycle of 45/55 for Processor clock and Audio clock

• Advanced, low-power CMOS process

• Industrial temperature range available

Block Diagram

Clock

Synthesis

Circuitry

USB Clock

Processor

Clocks

25 MHz

Crystal or Clock

Audio Clock

20 MHz

3

OE (all outputs)

25 MHz

Crystal

Oscillator

X1/ICLK

X2

PSEL1:0

ASEL

USEL

VDD

3

2

GND

2

Optional crystal

capacitors