ICS343

FIELD PROGRAMMABLE TRIPLE OUTPUT SS VERSACLOCK SYNTHESIZER

EPROM CLOCK SYNTHESIZER

IDT® / ICS™ FIELD PROGRAMMABLE TRIPLE OUTPUT SS VERSACLOCK SYNTHESIZER 2

ICS343

REV M 090613

Pin Assignment

8-pin (150 mil) SOIC

Output Clock Selection Table

Pin Descriptions

External Components

Series Termination Resistor

Clock output traces over one inch should use series

termination. To series terminate a 50 trace (a commonly

used trace impedance), place a 33 resistor in series with

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

The nominal impedance of the clock output is 20.

Decoupling Capacitor

As with any high-performance mixed-signal IC, the ICS343

must be isolated from system power supply noise to perform

optimally.

A decoupling capacitor of 0.01µF must be connected

between VDD and the PCB ground plane.

Crystal Load Capacitors

The device crystal connections should include pads for

small capacitors from X1 to ground and from X2 to ground.

These capacitors are used to adjust the stray capacitance of

the board to match the nominally required crystal load

capacitance. Because load capacitance can only be

increased in this trimming process, it is important to keep

stray capacitance to a minimum by using very short PCB

traces (and no vias) between the crystal and device. Crystal

capacitors must be connected from each of the pins X1 and

X2 to ground.

Example: For a crystal with a 16 pF load capacitance, each

crystal capacitor would be 20 pF [(16-6) x 2] = 20.

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. Distance of the ferrite bead and bulk decoupling

from the device is less critical.

2) The external crystal should be mounted just next to the

device with short traces. The X1 and X2 traces should not

be routed next to each other with minimum spaces, instead

they should be separated and away from other traces.

X1 / I C L K

VDD

GN D

PDT S

CL K 1

CL K 2

CL K 3

X2

1

2

3

4

8

7

6

5

CLK2

CLK2

CLK3

Output

Frequency

User

Configurable

User

Configurable

User

Configurable

Spread

Amount

User

Configurable

User

Configurable

User

Configurable

Pin

Number

Pin

Name

Pin

Type

Pin Description

1

X1/ICLK

XI

Connect this pin to a crystal or external clock input.

2

VDD

Power

Connect to +3.3 V.

3

GND

Power

Connect to ground.

4

CLK1

Output

Clock output. Weak internal pull-down when tri-state.

5

CLK3

Output

Clock output. Weak internal pull-down when tri-state.

6

CLK2

Output

Clock output. Weak internal pull-down when tri-state.

7PDTS

Input

Powers down entire chip. Tri-states CLK outputs when low. Internal pull-up.

8

X2

XO

Connect this pin to a crystal, or float for clock input.