www.teamwavelength.com
© 2007
LDTC0520 / LDTC1020
PAGE 16
LDTC1020-00400-A Rev B
FL OPERATION
Recommended order of setup:
Complete the WTC temperature control section
THEN the FL laser diode driver. Use a
simulated laser diode load until you are
comfortable with the FL operation.
1. SELECT MODE OF OPERATION
The two modes of operation supported by
the LDTC are Constant Current (CC) and
Constant Power (CP).
It is very important to
note that the LDTC operating mode should
be confi gured BEFORE applying power.
Changing operation mode while the LDTC is
operating can result in damage to your laser
diode.
In Constant Current mode, the setpoint voltage
input correlates directly to the laser diode
current, regardless of laser diode optical power
intensity. In Constant Power mode, the LDTC
controls the laser diode using the photodiode
to achieve a laser light intensity that is directly
proportional to the setpoint voltage.
Select the mode of operation by setting the
CC | CP
switch to the OFF position (INT)
for Constant Current mode or the ON position
(EXT) for Constant Power mode. See Figure 7
for switch setting details.
2. ATTACH THE FL POWER SUPPLY
The control electronics for the FL500(s) as
well as the laser diode current are supplied
by the VDD_FL power supply. The VDD_FL
power supply connection is pin 1 of the J1
power supply connector. This voltage should
be between +3 and +12 Volts. The VDD_FL
supply should be capable of supplying at least
1.5 Amps of current in applications that use
separate VDD_WTC and VS supplies. For
applications that tie the three power supplies
together use a power supply that is capable of
providing at least 3.5 Amps of current.
Performance of the laser driver is dependent
upon the operational characteristics of the power
supply. The LDTC provides minimal power
supply fi ltering and noise suppression. Care
should be taken to select a power supply with
suffi ciently low noise and ripple specs for your
application.
Online Safe Operating Area (SOA) calculators
are available for the FL500. Calculate the
maximum power dissipation of your design at
http://www.teamwavelength.com/
tools/calculator/soa/defaultld.htm
before applying
power to the LDTC.
Figure 7
Constant Current / Constant Power Switch
LDREF
C
C
| CP
TREF
EXT
INT
LDREF
C
C
| CP
TREF
EXT
INT
Constant Current
Constant Power
