ICS650-21

System Peripheral Clock Source

MDS 650-21 A

1

Revision 010301

Integrated Circuit Systems, Inc. • 525 Race Street • San Jose •CA•95126• (408) 295-9800tel • www.icst.com

PRELIMINARY INFORMATION

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.

The ICS650 can be mask customized to produce

any frequencies from 1 to 150 MHz.

Block Diagram

Description

Features

• Packaged in 20 pin tiny SSOP (QSOP)

• Lower jitter version of ICS650-01

• Operating VDD of 3.3V or 5V

• 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

Crystal

Oscillator

Clock

Synthesis

Circuitry

Output

Buffer

USB Clock

Output

Buffers

Audio Clock

Processor Clocks

(Fast Ethernet,

SCSI, PCI )

Output

Buffer

2

PSEL1:0

25 MHz

crystal

or clock

X1/ICLK

X2

25 MHz

Output

Buffer

3

ASEL

USEL

20 MHz

Output

Buffers

Output Enable (all outputs)