M61880FP

Rev.1.0, Sep.19.2003, page 2 of 20

Block Diagram

1

3

4

5

6

7

8

11

17

19

DATA

GND1

Switching current

source

(Isw)

100mA max∗

Bias current

source

40mA max∗

VCC1, GND1: For IC internal analog system

VCC2, GND2: For IC internal digital system

GND2

ENB

12

15

13

2

9

20

16

14

RO

LD

PD

S/H

Sample-and-hold

control input

Vr

Reference voltage input

Monitoring load resistance

connection pins

Comparator

Sample-and-hold circuit

Reference

voltage

source

Current switching

circuit

Monitoring photodiode

current input

Laser current

output

Reference voltage

output

Laser current

load resistance

Switching data input

Power supply 1

Power supply 2

Ground 1

Ground 2

Laser current enable

control input

Hold capacitance

connection pin

Switching current setting

resistance connection pin

Bias current setting

voltage input

Bias current setting

resistance connection pin

2RM

1RM

Function Overview

The M61880FP is a semiconductor laser diode driver/controller that automatically performs drive and laser power

control of a type of semiconductor laser diode in which the semiconductor laser diode (LD) anode and monitoring

photodiode (PD) cathode are connected to the stem.

Laser power control operation is performed by connecting an external capacitance to the CH pin and applying a

reference voltage to the Vr pin.

The PD current resulting from LD light emission flows to a resistance connected between 1RM and 2RM, and

generates a voltage (VM). This VM voltage is compared with the voltage applied to the Vr pin, and if VM < Vr, the

current from the CH pin is taken as a source current and an external capacitance is charged.

If VM > Vr, the current from the CH pin is taken as a sink current and the external capacitance charge is discharged.

This operation is performed when

S/H input = “L” and DATA input = “L” (sampling). When S/H input = “H”, the CH

pin goes to the high-impedance state (hold) irrespective of the state of VM, Vr, and the

DATA input.

The LD drive current is composed of switching current ISW controlled by

DATA input and LD bias current IB

unrelated to the

DATA input state.