lda1-cp2 Analog Technology, Inc., lda1-cp2 Datasheet - Page 2

• Manufacturer Part Number: lda1-cp2
• Description: Dual Mode Laser Driver
• Manufacturer: Analog Technology, Inc.

SPECIFICATIONS
Table 2 Characteristics (T
Maximum output current
Maximum output voltage on LDA
Laser current and power indication
voltage
Laser current indication absolute
accuracy
Laser current set-point voltage
Laser power set-point voltage
Laser driver efficiency
Current output noise
Rise time of current mode
Rise time of power mode
Power supply input voltage
Output reference voltage
Operating temperature
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10
11
12
13
14
15
16
6
7
8
9
Analog Technologies
SYNCO
Parameter
PGND
PGND
GND
PDA
LDA
LPO
VPS
LIO
LPS
LIS
ambient
Analog
Analog
Analog
Analog
Analog
Analog
ground
ground
ground
Digital
output
Signal
output
output
Power
Power
Power
output
input
input
input
input
= 25°C)
0.9 × Vps
Laser current set-point voltage. 0V to 2.5V sets the output current from 0 to 2A linearly.
The input impedance of this pin is 100KΩ. This pin can be set by an external analog
signal source, such as the output of a closed-looped op-amp, POT, or DAC.
Laser current output indication. 0V to 2.5V indicates the laser current of from 0A to 2A
linearly.
Laser power set-point voltage. 0V to 2.5V sets the laser output power from 0 to the
maximum value linearly. The input impedance of this pin is 100KΩ. This pin can be set
by an external analog signal source, such as the output of a closed-looped op-amp, POT,
or DAC.
The same as Pin 4
Laser power output voltage. Low impedance output. This is the output of the TIA (Trans-
Impedance Amplifier) for the photodiode in the laser. The trans-impedance is set by an
external resister R1 between PDA (pin 11) pin and GND (pin 9). See the schematic in
Figure 4 or Figure 5 below. Please note: V
Photodiode anode. This is the negative input of the TIA. See Pin 10 description and
Figure 4 or Figure 5 for the usage of this pin. If the PD’s capacitance exceeds 10pF, put a
capacitor of about the same value in parallel with R1 for compensation.
Laser diode anode. Connect it to the anode of the laser diode. 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. See Figure 4 or Figure 5.
Power ground pin. Connect it directly to the laser’s cathode which is also the case of the
laser. See Figure 4 or Figure 5.
Power ground pin. Connect it directly to power supply return rail.
Power supply voltage. The driver works from 3.0V to 6.0V.
Synchronization output. This pin can be used to synchronize another switch mode driver
such as for a TEC (Thermo-Electric Cooler) or a power supply so that the other drivers
will not interfere with this laser driver. The switching frequency is set at 700 KHz. There
is a 10K resistor between this pin and the switcher output. This pin can also be used to
see the switcher’s output voltage, see measure its duty cycle and magnitude.
3.0 ~ 6.0
0 ~ 2.5
0 ~ 2.5
0 ~ 2.5
±0.5%
Value
0.05%
0 ~ 85
≥90%
100
2.5
2
2
RMS@2A
Unit/Note
ms
°C
μs
A
V
V
V
V
V
V
-
-
CALIBRATE THE TIA TRANS-IMPEDANCE
Since the relationship between the output current of the PD
(Photo Diode) inside the laser and the output laser power
varies greatly from different laser diodes, the trans-
impedance of the TIA needs to be calibrated to match the
laser diode’s need.
The calibration procedure is as follows:
Read the laser diode datasheet carefully. According to the
laser power needed, find the corresponding current at room
temperature. Let’s call it Normal Operating Current, NOC.
Set the laser driver to output 1.2 times the NOC (See the
description about LIS (pin 6)). For example, if 200mA NOC
is needed for outputting a desired laser power of 100mW, set
the laser driver to output 240mA current, i.e., set
LIS = 2.5V × 0.24A/2A = 0.3V.
LPO
Dual Mode Laser Driver
= 2.5V – V
PDA
(V
PDA
LDA1-CP2
≤ 1V).
2