TLF11920

December 1995

CGS701AV

Commercial Low Skew PLL 1 to 8 CMOS Clock Driver

CGS701ATV

Industrial Low Skew PLL 1 to 8 CMOS Clock Driver

General Description

CGS701A is an off the shelf clock driver specifically de-

signed for today’s high speed designs It provides low skew

outputs which are produced at different frequencies from

three fixed input references The XTALIN input pin is de-

signed to be driven from a 25 MHz – 40 MHz crystal oscilla-

tor

The PLL using a charge pump and an internal loop filter

multiplies this input frequency to create a maximum output

frequency of four times the input

The device includes a TRI-STATE

control pin to disable

the outputs This feature allows for low frequency functional

testing and debugging

Also included is an EXTSEL pin to allow testing the chip via

an external source The EXTSEL pin once set to high caus-

es the External-Clock

MUX to change its input from the

output of the VCO and Counter to the external clock signal

provided via SKWTST input pin

(continued)

Features

Y

Guaranteed

outputs

Y

Pentium

Y

g

300 ps propagation delay

Y

Output buffer of eight drivers for large fanout

Y

25 MHz – 160 MHz output frequency range

Y

Outputs operating at 4X 2X 1X of the reference fre-

quency for multifrequency bus applications

Y

Selectable output frequency

Y

Internal loop filter to reduce noise and jitter

Y

Y

Low frequency test mode by disabling the PLL

Y

Implemented on National’s Core CMOS process

Y

Y

Y

28-pin PLCC for optimum skew performance

Y

Guaranteed 2k volts ESD protection

Connection Diagram

Pin Assignment for PLCC

TLF11920 – 1

Pin Description

PLCC Package

Pin

Name

Description

2

FBK IN

Feedback Input Pin

3

CLK4

4X Clock Output

5

XTALIN

Crystal Oscillator Input

6

GND

Digital Ground

7

FBK OUT

Feedback Output Pin

9

CLK1

l

1X Clock Output

10

GND

Digital Ground

11

CLK1

2

1X Clock Output

12

TRI-STATE

Output TRI-STATE Control

13

SKWTST

Skew Testing Pin

14

CLK1

3

1X Clock Output

15

GND

Digital Ground

16

CLK1

4

1X Clock Output

17

18

SKWSEL

Skew Test Selector Pin

19

GNDA

Analog Ground

20

21

EXTSEL

External Clock MUX Selector

22

GND

Digital Ground

23

CLK1

5

1X Clock Output

24

25

CLK1

0

1X Clock Output

26

CLK1SEL

CLK1 Multiplier Selector

27

GND

Digital Ground

28

CLK2

2X Clock Output

Pentium

is a registered trademark of Intel Corporation

TRI-STATE

is a registered trademark of National Semiconductor Corporation

C1996 National Semiconductor Corporation

RRD-B30M106Printed in U S A

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