Is this a suitable laser diode driver?

Thread Starter


Joined Sep 26, 2019

I am trying to make a three channel RGB laser diode driver with analog modulation. I would like to run all diodes off 12V, avoiding inefficient linear regulators. The modulation voltage should be 0-5V, and diodes running at 300mA or less.

I found a chip I think will work, AL8860, a DC/DC switching regulator with analog control ability. I have made the following schematic which I think should work for me.

The AL8860 uses 0.3V-2.5V/0-100% output current signal. I've added a simple resistor divider to bring the input signal in range. I have also added a trimmer potentiometer, this should let me fine tune the current down a little bit as required at the cost of resolution.

Laser diodes are not as tolerant to spiking current quite like a LED, so I am worried about switching currents. The datasheet specifies 0.25*Output Current. Is this a built in function of this regulator, or can I decrease peak currents by using a larger inductor and input decoupling capacitor?

I halfway know this will work, I bought a RGB laser module off ebay with "analouge modulation" that uses three MT7201 LED drivers for powering the laser diodes. Unfortunately, the modulation range is much lower, 0.3-1.3V/0-100% output current. It works, and has for a while, but the color resolution leaves a lot to be desired!

Thanks for reading, and for any advise!