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2
DBD-R2V1
Analog Technologies, Inc.
Pin 6
LIO, laser current output indication, analog output. 0V to 2.5V indicates the laser current of from
0 to 200mA linearly.
Pin 7
LPS, laser power set-point voltage, analog input. 0V to 2.5V sets the laser output power from 0 to
the maximum value linearly. The input impedance of this pin is 20K
Ω. This pin can be set by an
external analog signal source, such as the output of a closed-loop op-amp, POT, or DAC, or set by
the internal DAC A and leave this LPS pin unconnected. The internal DAC is connected to the
reference voltage 2.5V, so that its full scale is 2.5V.
Pin 8
LPI, laser power feedback input, analog input. High impedance input. The (positive-going) output
of an external power sense photodiode amplifier should be connected to this pin. Maximum
power for a given laser diode should correspond to 2.5 V.
Pin 9
LDA, laser diode anode, analog output. This pin is used to drive a laser of which the cathode is
connected to the case and the case is connected to the ground. When using this pin, the laser
anode needs to be connected to the ground. See Figure 1A.
Pin 10 LDC, laser diode cathode, analog output. This pin is used to drive a laser of which the anode is
connected to the case and the case is connected to the ground. When using this pin, the laser
cathode needs to be connected to the ground. See Figure 1B.
Pin 11 GND, ground. Connect laser anode or cathode to here.
Pin 12 GND, ground. Connect power supply return rail to here.
Pin 13 VPS, power supply, analog power input. The driver works at 5.0V.
Pin 14 SCK, serial interface clock, high impedance digital input. See Linear Tech LTC1654 data sheet.
Pin 15 SDI/MIND, serial data input/mode indication, digital input and output. The input impedance is
20K
Ω. When used as an output, a HI (=VPS) indicates constant current mode operation and a LO
(=GND) indicates constant power mode. When used as an input, is the data input to the serial
interface DACs. See Linear Tech LTC1654 data sheet.
Pin 16 CSLD, control/serial port/load, high impedance digital input. This pin is the DACs’ input for
serial interface enable and load control. See Linear Tech LTC1654 data sheet.
Mode Setting
A. Set the driver to constant current mode without over power protection
Under this mode, the laser is always operating at constant current mode.
1. Set LIS = 2.5V
× I
laser 4 200mA, where Ilaser is the set-point laser current. LIS can be set by the
way described in the pin description section.
2. Set LPS to 2.5V reference and connect LPI pin to ground. LPS can be set by the way described in
the pin description section.
B. Set the driver to constant current mode with over power protection
Under this mode, the laser is operating at the constant current mode unless the laser output power reaches
the preset maximum power. When the laser output power reaches the protection power, the laser will be
operating at a constant power mode.
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