iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 6/12
APPLICATIONS INFORMATION
Laser Power Adjustment
The pin ISET is used for the adjustment to the sensi-
The iC-WJB device can be adapted to CW laser diodes tivity of the monitor diode and to set the desired optical
of up to 40 mW. When the supply voltage is higher than laser power. The setpoint for the averaging control of
approx. 4.5 V, LD models in common cathode configu- the monitor diode current is pre-set at this pin.
ration can be used.
C1
47uF
5
DRIVER STAGE
1
+5V
VCC
3
REF
REFERENCE
C3
2nF
LD
MD
THERMAL
4
ISET
SHUTDOWN
8
7
KLD
RSET
24kΩ
R1
0..2Ω
VCC
INPUT
POWER DOWN
2
REF
AMD
6
IN
1
3
4
WATCHDOG
iC−WJB
CWD
CI
GND
2
3
1
CI
470nF
Figure 1: Circuit diagram for LD models with a common cathode
To calculate the current required at ISET, the average At Pav = Pcw = 1 mW, the monitor diode current is
optical laser power is to determine:
0.25 mA and RSET is calculated to:
twhi
Pav = Ppeak
∗
T
CR1∗V(ISET) 3∗1.22V
= 14.64kΩ
RSET =
=
Iav (AMD)
0.25mA
with peak value Ppeak and pulse/period duration twhi/T.
twhi
twlo
T
with Electrical Characteristics No. 301 for V(ISET) and
No. 107 for current ratio CR1.
Example for pulse operation
Pulse duty factor twhi/T set to 20 % at Ppeak = 3 mW,
laser diode as above with maximum optical output of
3 mW, monitor diode with 0.75 mA at 3 mW.
Figure 2: Duty cycle
Example for CW operation
The average optical power is set to 0.6 mW by the
Pcw = 1 mW (pin IN at VCC, pin CWD open), laser pulse duty factor; the average monitor diode current
diode maximum optical output of 3 mW, monitor diode IAV is then 0.15 mA. The resistor RSET is calculated
with 0.75 mA at 3 mW.
to:
ICHAUS [ IC-HAUS GMBH ]
