ICS650-21

SYSTEM PERIPHERAL CLOCK SOURCE

CLOCK SYNTHESIZER

IDT™ / ICS™ SYSTEM PERIPHERAL CLOCK SOURCE

3

ICS650-21

REV J 051310

External Components

The ICS650-21 requires a minimum number of external

components for proper operation.

Decoupling Capacitor

Decoupling capacitors of 0.01µF must be connected

between each VDD and GND (pins 4 and 6, pins 16 and 14),

as close to the device 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 outputs and the

loads are over 1 inch, series termination should be used. To

series terminate a 50

Ω trace (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.

Crystal Information

The crystal used should be a fundamental mode (do not use

third overtone), 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 - 6) x 2

In the equation, CL is the crystal load capacitance. So, for a

crystal with a 16pF load capacitance, two 20 pF [(16-6) x 2]

capacitors should be used.

13

OFF/14.318M

Output

14.31818 MHz clock output only when ASEL = VDD.

14

GND

Power

Connect to ground.

15

ASEL

Input

ACLK select pin. Determines frequency of audio clock per table above.

16

VDD

Power

Connect to VDD. Must be same value as other VDD. Decouple with pin 14.

17

PCLK3

Output

PCLK output number 3 per table above.

18

PCLK2

Output

PCLK output number 2 per table above.

19

PSEL0

Input

Processor select pin #0. Determines frequencies on PCLKs 1-3 per table

above.

20

PSEL1

Input

Processor select pin #1. Determines frequencies on PCLKs 1-3 per table

above.

Pin

Number

Pin

Name

Pin

Type

Pin Description