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6

Analog Technologies

ATLS4A217

High Voltage Constant Current 4A Laser Driver

Figure 6.

Both LISH and LISL pin set the output current without any

offset voltage. The relationship between the voltage and the

output current is:

respectively, in volt.

The LIO port, pin 10, outputs an analog voltage that is

proportional to the actual output current. When the output

current is 0A, the LIO voltage is 0.1V; when output current is

4A, the LIO voltage is 2.5V. The relationship is:

The waveform of LIO vs. LISH, LISL and PCN is shown in

Figure 8.

The output stage is designed to achieve low noise, high

efficiency, and relatively high modulation speed. It has an over

current protection circuit. There is a soft start circuit which

increases the output current slowly at the start up time and shuts

down the current quickly.

The LPGD pin indicates the control loop status. When this pin

goes high, >2V, the control loop is working properly, i.e., the

when this pin goes low, <0.3V, the laser driver is not working

properly, there might be a short or open circuit at the output, or

the laser driver is protected by the over temperature protection

circuit.

Figure 5. 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