ICS581-01, -02

Zero-Delay Glitch-Free Clock Multiplexer

MDS 581-01, 581-02 A

4

Revision 041100

Printed 11/14/00

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

A typical application for the ICS581-02 is to provide a backup clock for a system. The backup, reliable clock

would be connected to INB while the main clock would be connected to INA. If the main clock failed, the

backup clock would automatically be switched in. The following example shows the connection for this.

S0

S1

VDD

INA

INB

GND

FBIN

OE0

DIV

VDD

CLK1

CLK2

GND

OE1

CLK3

CLK4

VDD

0.01µF

0.01µF

33

Ω

In this example, the clocks are 155 MHz and so the frequency range is address 11. Both S0 and S1 are left

unconnected and so the on-chip pull-ups give the required high inputs. Similarly for OE0, OE1 and DIV. In

this example, CLK4 is used as the feedback.

External Components

The ICS581-01 and -02 require two 0.01 µF capacitors between VDD and GND, one on each side of the

chip. These must be close to the chip to minimize lead inductance. Series termination resistors of 33

Ω can

be used on the outputs. These also should be close to the chip, with the feedback connection after the

resistor.

MAIN

BACKUP

Application Example

33

Ω

33

Ω