Good IC but how to use it

[haydar1984]

I found this voltage regulator IC AP7217A-33 in the card of dvd writer , I read it's data sheet and think it's very good for use with the dvd burner LD and only one Li-ion is needed , but I'm not good with electronics and don't know how to limit the current , any ideas ?

 

[Fiddy]

not a real good regulator, the big killer is its fixed at 3.3V, which is a bit too high for red diodes and i dont know how to make it a current regulator, best off to buy a LM317 and make a DDL driver.

 

[haydar1984]

I have LM317 but it has too much voltage drop that can't be used with one battery , the 3.3 volts is on the high end but I'm planning on a big heat sink and making a burning laser with 250-300 watts so I think anything lower than 3.3 volts would be useless , also it came from the dvd writer board which drives the same diode for burning dvd's so I guess it's OK , any way I don't know exactly how to limit the current although it should be very simple for knowledable ppl here , It must be a resistor between two pins like all linear voltage regulators but I don't know which pins, hope someone will tell me

 

[Things]

A fixed voltage regulator will not work for laser diodes. They need to be constant current limited, which you can't do with a fixed regulator. They are cheap, just buy a better adjustable one.

 

[haydar1984]

Thanks for this info but i wonder why they used it in the dvd drive board?

 

[Things]

Because there are other electronics that need a stable regulated voltage too. If you search around a bit more, you'll probably find a small IC that'll be the laser driver. But it's not useful in our application.