iC-VJ, iC-VJZ

LASER DIODE CONTROLLER

Rev A1, Page 6/10

DESCRIPTION OF FUNCTIONS

Laser Power Adjustment

The iC-VJ and iC-VJZ devices can be adapted to CW

laser diodes from 2 to 40 mW. Models can be used in

which the cathode of the monitor diode is connected to

the anode or the cathode of the laser diode.

The driver output, pin KLD, permits laser diode cur-

rents of up to 250 mA. In the event of a thermal over-

load due to excessive high power dissipation, the

driver is turned off.

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 average control of the

monitor diode current is preset at this pin, by connect-

ing it either to a resistor or a current source.

When connected to a current source, by means of an

operational amplifier with current output (OTA) for ex-

ample, the laser power can also be modulated. In or-

der to limit the current at pin ISET when turning on the

supply for the OTA, however, the OTA output should be

connected to the base point of RSET.

The maximum current possible at ISET must be taken

into consideration when dimensioning the capacitor

C2.

Example iC-VJ

Laser diode with 5 mW maximum optical output, mon-

itor diode with 0.13 mA/mW, average power 1 mW

(peak power 2 mW; pulse duty ratio Twhi / T is 50%).

RSET is calculated as:

RSET =

CR1 ∗ V (ISET )

I(AMD)

=

1 ∗ 1.22 V

0.13 mA

≈ 9.4 k Ω

with the Electrical Characteristics No. 501 for V(ISET)

and with No. 107 for current ratio CR1.

Example iC-VJZ

Laser diode with 5 mW maximum optical output, mon-

itor diode with 0.75 mA at 3 mW, average power 1 mW

(peak 2 mW; pulse duty ratio Twhi / T is 50%).

For the average monitor current of 0.25 mA the resistor

RSET is calculated as:

RSET =

CR1 ∗ V (ISET )

I(AMD)

=

3 ∗ 1.22 V

0.25 mA

≈ 14.6 k Ω

with the Electrical Characteristics No. 501 for V(ISET)

and with No. 107 (iC-VJZ) for current ratio CR1.

DC−Monitor

5V

Sync

16:1

NQ

NQ

Q

1

7

4

2

3

5

6

DRIVER

OSCILLATOR

POWER ON

TH−SHUTDOWN

DIVIDER

REFERENCE

MONITOR

OUTPUT

R1

800

Ω

C1

100pF

RSET

R3

10k

Ω

C2

470nF

C3

100nF

C4

100

µF

15

NPRF

9

CI

5

R

13

MO

11

ISET

4

MI

AMD

12

VCC

6

RC

3

GND

7

AGND

14

PRF

KLD

MD

LD

iC−VJ/VJZ

1:1 iC−VJ

1:3 iC−VJZ

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