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9

Analog Technologies

Low Noise Constant Current Laser Controller

ATLS200MA103

Figure 16. Driving High Voltage Laser Diodes

Driving High Voltage Laser Diodes

Some laser diodes have high forward voltage, such as 7V,

while the laser driver ATLS200MA103D has a maximum

output voltage of 4V. This section tells a way to drive such

laser diodes by using this laser driver.

The schematic is shown in Figure 16, where Power Supply

1 is the power supply for the laser driver, Power Supply 2

is for increasing the laser driver's maximum output voltage.

Please notice that the power on sequence has to be in this

way: turn on Power Supply 1, turn on Power Supply 2,

then turn on the laser driver by driving SDN (Shutdown)

pin to logic high.

The sequence for turning off the laser circuit is: turn off the

SDN pin by pulling it down to the logic low, turn off

Power Supply 1, then, turn off power supply 2.

To make sure the circuit works ok: turn on the laser,

measure LDA voltage, it should be between 1V to 3V, at

room temperature, the ideal LDA voltage is around 2V.

Figure 17. Controller Internal Temperature vs. TMPO Voltage

–20 –10

0

10

20

30

40

50

60

70

80

90

100

110

120 130

140

150

0.4

0.8

1.2

1.6

2.0

2.4

Voltage (V)

Temperature (°C)

A Linearized TMPO Voltage vs. Controller Temperature

Actual TMPO Voltage vs. Controller Temperature