laser diode driver circuit with 8bit digital control

[scriptster]

Hi, does anyone have a circuit diagram for a laser driver that can control the current into the diode from microcontroller digital outputs (8bit).

I need to build three drivers for my three diodes, 20x dvd, 6x bluray and the IR diode in a cheap 100mW green module. They will be controlled from an ATMega.

I'm using the old KES-400A sled to combine the 3 colors and make a very basic microcontroller driven RGV projector.

I understand it's probably too late a response for your particular project, but somebody else may be looking for the same thing, and that actually includes me although I need it for a different application. I just wanted to mention that there may already be a 10-bit DAC chip right there on the sled! If you unwrap the flex PCB, there may be an EL6935 chip there that's designed to drive two laser diodes (red and IR or blue and IR) and has a 10-bit DAC onboard. It's not a trivial matter of how to get to it due to this being a small 38-pin QFN package, but most of the schematic is already there (and in some cases you can leave one of the laser diodes soldered to the flex PCB) and you need something like 14 pins attached to your control circuit (make it 12 'cause you're looking for an 8-bit DAC, not 10).

I'm not familiar with the actual sled you've mentioned and some I've looked at had a driver IC (AN1333, LMH6525 and others) that's attached to an external DAC. But if you see this Intersil's chip (EL6935, any modification - ACL, BCL etc.) you may have something like 75% of the circuit you're looking for right there.

Good luck!

[scriptster]

you need something like 14 pins attached to your control circuit (make it 12 'cause you're looking for an 8-bit DAC, not 10).

Just wanted to add that the DAC is parallel, not serial, hence the number of connections. So it can let you control it quicker but the flip side of course is tying up so many I/O ports...

[Psi]

I understand it's probably too late a response for your particular project

i got distracted with other projects and the lasers/optics are still sitting in a draw.

I don't think i have the sled electronics any more, but that's a good point about a driver chip already being there.