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PLTB450B puts out only a flash

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I managed to get it to work with the LPC-815, first I turned it on with the LD connected set to 400mA, then I measured the voltage across the LD, I got 3V. Next step was to set the voltage trimpot to 3V.

Using the osciloscope I seen that when the TTL goes high, it aplies whatever voltage was set on the voltage regulator, then, it starts regulating the current, so the solution was to limit the output voltage to the max voltage the LD takes at 400mA, so when the TTL goes high, it aplies 3V, that is safe, I got it running and tested. So I let this as a advertisement.
 

Cyparagon

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when the TTL goes high, it aplies 3V, that is safe,
Wrong. That means it is being driven in constant voltage mode. You may get lucky a few times, then pop it a few days down the road. The forward voltage drop of a diode varies with temperature and current. 3V does NOT mean 400mA across it.
 
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So, what kind of damage can occur? If the diode starts draining more current, then the voltage will be reduced by the current regulator.
 

Cyparagon

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You said so yourself there is a lag before the current regulation kicks in. That's been my finding on these types of boards as well. I've seen delays as long as half a second. It only takes microseconds for damage to occur.
 
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Yeah, that's true, I don't recommend this board, I still using it because is powering a LPC-815 and I have 5 more of it in cause that one gets damaged.
 




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