ICS180-01

LOW EMI CLOCK GENERATOR

SSCG

IDT™ / ICS™ LOW EMI CLOCK GENERATOR

3

ICS180-01

REV D 051310

External Components

The ICS180-01 requires a minimum number of external

components for proper operation.

Decoupling Capacitor

A decoupling capacitor of 0.01µF must be connected

between VDD and GND on pins 6 and 3, as close to

these pins as possible. For optimum device

performance, the decoupling capacitor should be

mounted on the component side of the PCB. Avoid the

use of vias in the decoupling circuit.

Series Termination Resistor

When the PCB trace between the clock output and the

load is over 1 inch, series termination should be used.

To series terminate a 50

Ωtrace (a commonly used trace

impedance) place a 33

Ωresistor in series with the clock

line, as close to the clock output pin as possible. The

nominal impedance of the clock output is 20

Ω.

value of these capacitors is given by the following

equation:

PCB Layout Recommendations

For optimum device performance and lowest output

phase noise, the following guidelines should be

observed.

1) The 0.01µF decoupling capacitor should be mounted

on the component side of the board as close to the VDD

pin as possible. No vias should be used between the

decoupling capacitor and VDD pin. The PCB trace to

VDD pin should be kept as short as possible, as should

the PCB trace to the ground via.

2) To minimize EMI, the 33

Ωseries termination resistor

(if needed) should be placed close to the clock output.

3) An optimum layout is one with all components on the

same side of the board, minimizing vias through other

signal layers. Other signal traces should be routed away

from the ICS180-01. This includes signal traces just

underneath the device, or on layers adjacent to the

ground plane layer used by the device.