Laser Diode Driver: dampening a voltage spike

High everyone,

I'm making a laser-diode driver circuit with an enable that accepts 5[V] logic. It's a constant-current supply (from the LT1083 adjustable voltage regulator) to power the laser, a mosfet acting as a switch to turn on the constant current supply, and a mosfet driver IC.


The mosfet is an N-channel mosfet driven with the LT1910 high-side driver.

Right now, I'm simulating a circuit just like this in LTSpice using an LED with comparable voltage-drop and current ratings.

The problem I'm getting is that I'm seeing a voltage spike at the diode's anode, and it's just enough current and voltage to fry the sensitive laser diode. Does anyone know a way to dampen that spike? I've attached an image of the circuit and waveforms below.

Thanks in advance for taking a look!

Are you modulating the diode ? If not then try a 100nF capacitor across it and see if it helps.

Try adding a 100uH inductor in series with R1.

Thanks alec_t and picbits. Adding that 100uH inductor in series did the trick exactly.

hi

you really want a V2 rise time of 500ms?

eT