ICS556-03 datasheet(3/8 Pages) ICST

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MDS 556-03 B

Revision 030204

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Quad LVDS Oscillator/Buffer

ICS556-03

External Component Selection

The ICS556-03 requires a minimum number of external

components for proper operation.

Decoupling Capacitors

A decoupling capacitor of 0.01

µF should be connected

between VDD and GND on pins 2 and 10 as close to

the ICS556-03 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.

LVDS Driver Termination

A general LVDS interface is shown in Figure 2. In a 100

ohm differential transmission line environment, LVDS

drivers require a matched load termination of 100

across near the receiver input. For a multiple LVDS

outputs buffer, if only partial outputs are used, it is

recommended to terminate the un-used outputs.

Quartz Crystal

The ICS556-03, a quad 25 MHz LVDS Clock utilizes an

external crystal to generate 4 pairs of low phase noise

outputs. The crystal should be a fundamental mode,

parallel resonant. Crystal capacitors should be

connected from pins X1 to ground and X2 to ground to

optimize the initial accuracy. The value of these

capacitors is given by the following equation

Crystal Caps (pf)= (CL-12)x2

In the equation, CL is the crystal Load capacitance. So

for the crystal with 16pF load capacitance, two 8

pF[(16-12)x2] capacitors should be used.

The external crystal must be connected as close to the

chip as possible and should be on the same side of the

PCB as the ICS556-03. There should be no via’s

between the crystal pins and the X1 and X2 device

pins. There should be no signal traces underneath or

close to the crystal.

Output

Differential clock output.

EN3

Input

Enable pin for Outputs C and C. EN4 high enables C, C outputs.

EN3 low tri states C, C outputs.No Pull-Up resistor.

EN4

Input

Enable pin for Outputs D and D. EN4 high enables D, D outputs.

EN4 low tri states D, D outputs.No Pull-Up resistor.

Number

Name

Type

Pin Description

100 ohm

2.5V

100 Ohm Differential Transmission Line

LVDS_Driver

Figure 2. Typical LVDS Driver

Termination

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