iC-WJ, iC-WJZ

LASER DIODE DRIVER

Rev C1, Page 6/12

APPLICATIONS INFORMATION

Laser Power Adjustment

The iC-WJ and iC-WJZ devices can be adapted to CW

laser diodes from approximately 2 to 40 mW. N- and

M-type models can be used.

The pin ISET is used for the adjustment to the sensi-

tivity of the monitor diode and to set the desired optical

laser power. The setpoint for the averaging control of

the monitor diode current is preset at this pin.

MD

LD

+5 V

DRIVER

INPUT

POWER DOWN

THERMAL

WATCHDOG

REFERENCE

REF

VCC

REF

1

2

3

4

470 nF

CI

RSET

74HCxx

100 uF

C1

AMD

7

ISET

4

GND

1

IN

6

CWD

2

CI

3

VCC

5

KLD

8

SHUTDOWN

iC−WJ/WJZ

1:1 iC−WJ

1:3 iC−WJZ

R1

12

Ω

C3

2 nF

Figure 1: Operation of a laser diode according to the example

To calculate the current required at ISET, the average

optical laser power is to determine:

T

twhi

T

twlo

Figure 2: Duty cycle

Example iC-WJ

Laser diode with 5 mW maximum optical output, mon-

itor diode with 0.13 mA/mW, pulse duty factor set to

The resulting average optical power is 1 mW and the

average monitor diode current is 0.13 mA. The resistor

RSET is calculated as:

RSET =

CR1 ∗ V (ISET )

=

1 ∗ 1.22 V

0.13 mA

= 9.4 k Ω

with the Electrical Characteristics No. 301 for V(ISET)

and No. 108 for current ratio CR1.

Example iC-WJZ

Laser diode with 5 mW maximum optical output, mon-

itor diode with 0.75 mA at 3 mW, CW operation (pulse