Help with dual red setup.

[dnar]

The tests above are not using a DAC. I am using a function generator. Purely testing the P3's. The max configured current is never exceeded. Pretty sure your problems lay elsewhere.

[magman116]

The tests above are not using a DAC. I am using a function generator. Purely testing the P3's. The max configured current is never exceeded. Pretty sure your problems lay elsewhere.

While I still haven't taken scope shots yet, I did the testing with a function generator. 5V signal, 10Khz modulation. I tested sin, square, and sawtooth waveforms. Each had a different result. Over all, the results were very comparable to what you got.

I then connected the DAC and displayed a test pattern. Looking at the modulation input and the driver output, the waveform is definitely a PWM waveform, both modulation and driver output waveforms were the same. There was a lot of noise and the output really started to look bad above 50khz.

dnar, would you please check your DAC output and tell me what you get?

[dnar]

Ok, I'll retest with my AUDIOLASE DAC. What DAC are you using?

[magman116]

Ok, I'll retest with my AUDIOLASE DAC. What DAC are you using?

I am using a Frame Screamer Express 2.0, FSX2.0

[drlava]

Nice scope shots, there. I especially like this one

that shows how the protection clips nicely when the input is overdriven.

With the 24V capture, there is a much larger discrepancy between the power supply voltage and the laser diode voltage, so the hump you see is the driver being more 'careful' at the peak to not to let the 24V supply spike the diode.

When driving LDOCs with 300ma or more, it's important to ensure the die is kept clean during assembly. any small dirt or smoke particle can lead to failure. What lenses are you using? Some can generate small back reflections.

[magman116]

Dr Lava,

I have added another FMP3 so each LOC has its own. I am not seeing the current spikes and all is well.

I am using O-like AR glass lenses for red.