Help identifying a part please? Audient id22

[mrclunk]

Any ideas i've search the usual places?

[This is a good one = http://www.s-manuals.com/smd]

It's a LDO reg i think. I don't have a schematic.

The marking is L J S R B U   

It's burning up, in circuit. I've a few things upstream i'll replace anyway but basically going to shotgun a few things..

 

[Khron]

That may well be an OnSemi NCP699 (marking LJS; the rest is the datecode), the 1.8V fixed variant.

https://www.onsemi.com/pub/Collateral/NCP699-D.PDF

You might want to check the diode-drop on its output (pin 5). If it's burning up, whatever it's supplying might be toast.

What interface is this from? Going by the Xmos MCU and the SMSC USB interface chip...

 

[mrclunk]

Amazing thanks!
You've nailed it.

It's from the USB / Power board of an Audient id22 interface.
Took a punt on a knackered one on eBay.

It may well be something down the line. It's currently pumping out 5V so somethings fishy.
I'll have another go at the weekend.
thanks

 

[Khron]

That doesn't sound too promising - feeding 5v into something expecting 1.8v is quite often kinda-sorta bad...

 

[Newmarket]

Without wishing to ask the obvious - have you asked Audient themselves ?

 

[mrclunk]

Without wishing to ask the obvious - have you asked Audient themselves ?

Whaaat, don't be silly...  Where's the fun in that!

I did have another go at it briefly and something, as yet unknown, is shorting to ground on the 1.8V line.
Not really set up for the tiny smt  ic packages on this...
The 1V8 line runs to the chip below REG3 any ideas what that is?
Do you use a heat gun to remove such ic?

I'm about to buy some new tools, some sort of DS, my analog scope is giving up,  and maybe now an excuse for re-work station.

 

[Khron]

Well, it says right on the chip - USB3318

And yes, that's a QFN package, that has a metal "belly pad", so hot air is necessary.

Odds are good(?) that's the only chip powered by that regulator, by virtue of the proximity, so you may or may not be lucky, and get away with "only" replacing that usb-interface chip.