Common diodes - maximum forward voltage?

[buffo]

Hey everyone;

Real quick, I need some data points for a project I'm working on. I'll explain later. I need the absolute maximum forward voltage drop one would ever expect to see when powering the following diodes at maximum current:

9 mm can 445 nm blue:

5.6 mm can 637 nm red (P-71's):

I *think* the 9mm 445 blue has a maximum forward voltage of as much as 5.7 volts, but I need to be sure.

As for the 637 nm reds, I think they're around 3.6 volts.

Can anyone confirm these numbers?

THANKS!

Adam

PS: I'm talking absolute maximum here. As in, you're being stupid and pushing 3 amps through that 9 mm 445... Not saying that the diode will last long at that point; I just need to know the max possible forward voltage under extreme conditions.

[-bart-]

You're in the right ballpark.

Expect some 100mv voltage drop over driver- and supplyleads under extreme conditions.

Don't forget voltagedrop across sense resistor

Always assume the worstcase dropout voltage when picking power transistors.

[buffo]

Thanks for the validation, Bart. I was reasonably certain we had accounted for everything, but I wanted a last "sanity check" before I make it official.

Adam

You're in the right ballpark.

Expect some 100mv voltage drop over driver- and supplyleads under extreme conditions.

Don't forget voltagedrop across sense resistor

Always assume the worstcase dropout voltage when picking power transistors.

[danielbriggs]

Adam,
Just an "FYI" the new green direction injection 520nm diodes, (50mW and 170mW), have a working forward V_f of 7.5V with a max of 8.0V run within spec.

However I'm not sure if that is of relevance to whatever "sekret pro(d)jectz" you are working on.

Cheers,
Dan

[StarryEyed]

520nm 170mW?????
Tell me more pls.

Cheers

[buffo]

Daniel;

Those new greens won't have the current draw though, so it should be fine. My main concern is someone trying to over-drive a 445 nm blue diode (or worse, a pair in parallel). Need to be sure I left enough headroom in the design...

It's not really a secret. I'm reviving the ancient diode driver project that Bill Benner developed over 4 years ago. But it had to be updated to reflect modern diodes. Just double-checking the math (which is a bit pointless now, since parts have already been ordered)...

Tell you all about it in Utila! (Might even have a sample to play with by then...)

Adam