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18

PLD10000/PLD12500 LASER DIODE DRIVER

TROUBLESHOOTING

PROBLEM

POTENTIAL CAUSES

SOLUTIONS

Driver will not switch on

Improperly configured power

supply

Carefully check the wiring diagram according to

Table 3. Make sure the

polarity of the power supply is correct.

Output will not enable

Remote Enable signal is not

correct

Refer to the LD Enable specifications in

Table 1 and make sure the

LD ENABLE (pin 22) signal is correct.

Laser output power too low in

Constant Current mode

Laser current setpoint too low

Increase the setpoint either by adjusting the I OUT ADJ trimpot clockwise, or

by increasing the signal voltage on the Analog Input (pin 16).

Laser current limit set too low

Refer to

page 11 for instructions on setting the laser driver current limit.

Laser drive is compliance limited

Check the laser diode specifications to determine the forward voltage (V

F).

Make sure that the PLD is not compliance limited. Refer to the Electrical

Specifications table on

page 5. If the driver is compliance limited,

V

LD Anode (pins 7, 8, 9) may need to be increased. Verify that the PLD will

be operating within the Safe Operating Area if the supply voltage is

increased.

Laser does not reach desired

output in Constant Power

mode

Current limit set too low

Check the laser diode datasheet to determine the approximate laser drive

current at the desired optical power output level. Then verify that the current

limit is set slightly higher than that. Refer to

page 11 for instructions on

setting the laser driver current limit.

Photodiode feedback current is

out of range for the PLD

Refer to the laser diode datasheet to determine the approximate photodiode

(PD) current at the desired output power level. If the PD current exceeds the

PLD PD current range, set the PD Range switch to High Range (Type A/B

laser diodes only.)

Voltage drop across cables is too

high

At high currents the voltage drop across the transmission wires may

become an issue. The excessive voltage drop may result in the driver being

compliance voltage limited before the drive current setpoint is reached. Use

large-gauge wires, and keep the wires as short as possible.