wart overvoltage protection (2023 Update)

But you don't know where it's been. It might not even be a real TI part.

Reply to
John Larkin
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søndag den 2. oktober 2022 kl. 20.05.14 UTC+2 skrev John Larkin:

it's LCSC not some dodgy ebay shop

Reply to
Lasse Langwadt Christensen

Coincidentally, I recently ordered a couple of hundred of those on spec, for like $66.

They are a bit suspicious in that the 100-piece price is considerably lower than TI's, but we'll see.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Reverse protection is also important to protect against an input short, which can blow up stuff by forcing currents from output to input.

That's one of the three ways to blow up a 317, and one of the two to blow up an 78xx regulator. (Input overvoltage is the other main one, and for a 317, discharging a big ADJ pin bypass backwards.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Would that be a 'sidactor'? This variant works for AC limiting, should be OK with a polyfuse in series about not hurting a 24 supply

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It has to be depowered completely to reset it, so the polyfuse will stay warm until unplugged. The breakover is built-in, rather coarse, so one hopes your nominal 12V box is OK with 15...

Reply to
whit3rd

** Yawwwwwnnnnn...........

** Drivel.

** Ship a dead $10 wall wart to you ?

Get f***ed.

....... Phil

Reply to
Phil Allison

A soft gate drive, like just a zener, can make an SCR chip fire locally, near the gate wirebond, and fry that region before conduction spreads laterally. It's like 2nd breakdown failure in transistors.

There are specific crowbar controller chips to make a hard, fast gate drive.

Look it up.

Reply to
John Larkin

I once mightily abused an LM317 adjust pin to see if I could break it. No feasible abuse did.

Reply to
John Larkin

100 uF ADJ bypass, 30V output, short input to ground. That'll do it.

Cheers

Phil Hobbs

Reply to
Phil Hobbs

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