Datasheet

iC-WJB
2.7 V LASER DIODE DRIVER
Rev E1, Page 10/12
2.7..6V
ISET
4
KLD
AMD
7
CI
3
CWD
2
GND
1
IN
6
LD MD
8
VCC
5
WDOG
REF
iC−WJB
VMOD
0..1.3V
R1
2nF
C3
CI
22nF
RSET
27kΩ
100nF
C2
C1
47uF
27kΩ
R3
0..2Ω
Figure 11: Analogue modulation during CW operation
Analogue modulation during CW operation
The modulation cut-off frequency is determined by the
capacitor CI as well as by the operating point set with
the resistor RSET. With CI = 100 nF and RSET = R3 =
15 kΩ the cut-off frequency is approx. 30kHz, with CI =
22 nF and the same resitor value of about 150 kHz.
The laser power can also be modulated by adapting a
current source, e.g. by using an operational amplifier
with a current output (OTA). To limit the current at pin
ISET while turning on the power supply for the OTA cir-
cuitry, however, RSET should be connected to the OTA
output (instead of to GND). The maximum current pos-
sible at ISET must be taken into consideration when
dimensioning the capacitor CI.
PC board layout
The ground connections of the external components
CI, CWD and RSET have to be directly connected at
the IC with the GND terminal.
DEMO BOARD
For the devices iC-WJ/WJZ/WJB a Demo Board is
available for test purpose. The following figures show
the schematic diagram and the component side of the
test PCB.