TLF12386

September 1995

CGS702V

Commercial Low Skew PLL 1 to 9 CMOS Clock Driver

with Improved EMI

General Description

The CGS702 is an off-the-shelf clock driver specifically de-

signed for today’s high speed processors It provides low

skew outputs which are produced at different frequencies

from three fixed input references The CGS702 is a reduced

EMI version of the CGS700 The XTALIN input pin is de-

signed to be driven from three distinct crystal oscillators run-

ning at 25 MHz 33 MHz or 40 MHz

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 while the PLL is still in lock This function allows

testing the board without having to wait to acquire the lock

once the testing is complete

(Continued)

Features

Y

Reduced EMI compared to CGS700 (refer to EMI

characteristics)

Y

Y

Y

Output buffer of nine drivers for large fanout

Y

25 MHz – 160 MHz output frequency range

Y

Outputs operating at 4x 2x 1x of the reference

frequency for multi-frequency 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

Symmetric output current drive

a

Y

28-pin PCC for optimum skew performance

Y

Guaranteed 2 kV ESD protection

Connection Diagram

Pin Assignment for PLCC

TLF12386 – 1

TRI-STATE

is a registered trademark of National Semiconductor Corporation

Pin Description

PLCC Package

Pin

Name

Description

2

SKWSEL

Skew Test Selector Pin

3

CLK4

4x Clock Output

5

XTALIN

Crystal Oscillator Input

6

GND

Digital Ground

7

CLK1

0

1x Clock Output

9

CLK1

1

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

EXTCLK

External Test Clock

19

GNDA

Analog Ground

20

21

EXTSEL

External Clock MUX Selector

22

GND

Digital Ground

23

CLK1

5

1x Clock Output

24

25

CLK1

6

1x Clock Output

26

CLK1SEL

CLK1 Multiplier Selector

27

GND

Digital Ground

28

CLK2

2x Clock Output

C1995 National Semiconductor Corporation

RRD-B30M105Printed in U S A