February 1998

ML4621

Data Quantizer

GENERAL DESCRIPTION

The ML4621 data quantizer is a low noise, wideband

monolithic IC designed specifically for signal recovery

applications in fiber-optic receiver systems. It contains a

two stage wideband limiting amplifier which is capable

of accepting an input signal as low as 2mV with a 55dB

dynamic range. This high level of sensitivity is achieved

by using a DC restoration feedback loop which nulls any

offset voltage produced in the limiting amplifier.

The output stage is a high speed comparator circuit with

both TTL and ECL outputs. An enable pin is included for

added control.

The minimum signal discriminator circuit provides a link

monitor function with a user selectable reference voltage.

This circuit monitors the peaks of the input signal and

provides a logic level output indicating when the input

falls below an acceptable level. This output can be used

to disable the quantizer and/or drive an LED, providing a

visible link status.

FEATURES

s

50MHz minimum bandwidth for data rates of up to

100MBd

s

Can be powered by either 5V providing TTL level

outputs, or -5.2V providing ECL level outputs

s

Low noise design: 25µV RMS over 50MHz noise

bandwidth

s

Adjustable link monitor function

s

Wide 55dB input dynamic range

s

10ns minimum input pulse

1

21

18

VIN+

VIN–

VDC

VREF

VTHADJ

GND

VCC TTL

GND TTL

TTL OUT

CMP ENABLE

VCC

CPEAK

ISET

INOM

CF1

VOUT+

VOUT–

A1

A2

DC

AMP

ECL

CMP

TTL

CMP

FILTER

REF

THRESHOLD

GENERATOR

CF2

MINIMUM

SIGNAL

DISCRIMINATOR

CMP+

ECL+

ECL–

CMP–

ECL LINK MON

TTL LINK MON

22

6

5

8

23

27

26

24

28

19

20

3

1

2

17

16

10

11

13

9

12

14

Please

See

ML4622/ML4624

for

New

Designs