M61880FP Ver la hoja de datos (PDF) - Renesas Electronics

Número de pieza

componentes Descripción

Fabricante

M61880FP

Laser Diode Driver/Controller

Renesas Electronics 

M61880FP

Pin Description

Pin No.

1

2

3

4

5

6

7

8

9

10

11, 12

13

14

15

16

17

18

19

20

Symbol

Rs

GND1

RB

VB

Vref

Vr

CH

S/H

Vcc1

NC

1RM

2RM

ENB

DATA

PD

GND2

LD

NC

RO

Vcc2

Name

Switching current setting

resistance connection pin

Ground 1

Bias current setting

resistance connection pin

Bias current setting voltage

input

Reference voltage output

Reference voltage input

Hold capacitance

connection pin

Sample-and-hold control

input

Power supply 1

NC

Monitoring load resistance

connection pins

Laser current enable input

Switching data input

Monitoring photodiode

current input

Ground 2

Laser current output

NC

Laser current load output

Power supply 2

Function

Connects switching object current (ISW) setting resistance to GND.

Internal analog GND

Connects bias current (IB) setting resistance to GND.

Leave this pin open when IB is not used.

Bias current value (IB) is set by applying a voltage to this pin.

Leave this pin open when IB is not used.

M61880 internal reference voltage (1.5 V typ.) output pin

Connected to non-reversed input pin of comparator in sample-and-

hold circuit. Connect this pin to Vref pin when using M61880

internal reference voltage.

Connects hold capacitance to GND. This pin is connected to

sample-and-hold circuit output and ISW current source input in

M61880.

Sampling when “H”, hold when “L”

Internal analog power supply. Connected to positive power supply

(+5 V).

Not connected to internal circuitry.

Connects load resistance for converting monitor photodiode current

to voltage between 1RM and 2RM. (1RM pin is connected to GND

in IC.)

When “H”, LD drive current source circuit is turned off. Also, CH

pin is forcibly fixed at “L” level.

ISW+IB current flows to laser diode when “+”, and IB current when

“H”.

Connects monitor photodiode anode.

Internal digital GND

Connects semiconductor laser diode cathode.

Not connected to internal circuitry.

Connects laser current load resistance to Vcc.

Internal digital power supply. Connected to positive power supply

(+5 V).

Operation

1. Laser drive current setting method

The laser drive current consists of switching current ISW + bias current IB.

(1) Switching current ISW setting method

a. Decide the maximum current value ILD(MAX) to flow in the laser diode (LD). This is decided taking account of

the LD type, dispersion, temperature changes, secular changes, etc.

b. Find ISW (initial set value) from the following equation.

ISW (initial set value) = ILD(MAX)/1.9

c. Find switching current setting resistance RS from the following equation.

RS [kΩ] 30 × Vref (1.5V) [V] / ISW (initial set value) [mA]

In this case the LD current can be controlled in a range of 10% to 90% of ISW (initial set value).

Rev.1.0, Sep.19.2003, page 3 of 20

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