D882 sot-89

[eccerr0r]

What the ...

I had the magic smoke come out of my universal pogo pin charger.
Was probing around the transistors on the board and found a D882, supposedly NPN, was not working as it should. Interesting.

First I looked up D882 and got a TO-126 device. No way. The device was SMT.

Then I found a SOT-89 D882. That's more like it.

Then I was reading the specs as I do not think I have any D882s on hand. I read on a datasheet from shenzen topsky:

Ic Max: 3A continuous (red flag alert right away...)
Pc Max: 500mW (reasonable for a SOT89)

Wait a minute.

Oh well, will have to look for one so I can fix this pogo universal Li-ion charger and hope nothing else is wrong, but the contradiction on the datasheet made me go wtf... there's no way to pass 3A continuous and still stay under 500mW dissipation...

[diif]

Re: D882 sot-89

A different manufacture uses the heading ABSOLUTE MAXIMUM RATING with this note below.
Note Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.

[sam_sam_sam]

Re: D882 sot-89

I have also found this to be some what confusing as well but I try use any device in its normal operating range and on the lower end of the range if possible

I looked up this charger and found that it has the following in its description “ Automatic polarity detection”

If yours has this capability be very careful using this function because you can destroy it
I have a charger that says that it can do this as well but there is a catch to this if you install battery in one direction and for what ever reason you change your mind and decide to reverse the direction you might fry the device that allows you hook it in either direction if you do not power it completely power off the device and let the circuit be completely discharge it’s self completely

I had decided to torture test this claim that it has this function “Automatic polarity detection” and what it would take to destroy this function and found that it can not take this abuse ( I have several of this type of charger ) but not the brand that you mentioned in this post

Automatic polarity detection is a great feature but it has its limitations to how you can use it

For what ever reason this warning has not been given for these devices that can do this function

[eccerr0r]

Re: D882 sot-89

Since passing 3A through would always exceed 500mW they may well just say 100000A is the limit because you'd exceed 500mW before getting close to that... If this was a MOSFET then things would be different, but not a BJT.

[eccerr0r]

Re: D882 sot-89

BTW yeah, it's probably what happened, the auto polarity probably got confused and tried to reverse charge...killing the transistor.

Which is a lot better than causing the battery to immolate...

As for what to do with this transistor... not sure. Surprised the D882 TO-126 and the SOT-89 have different characteristics...

[eccerr0r]

Re: D882 sot-89

Argh. I see the h-tree. Funny the magic smoke leaked out of something but I couldn't figure out what leaked - the nonfunctional D882 looks fairly intact and the rest of the h-tree looks ok...
hmm... another mystery to be solved...

[sam_sam_sam]

Re: D882 sot-89

Argh. I see the h-tree. Funny the magic smoke leaked out of something but I couldn't figure out what leaked - the nonfunctional D882 looks fairly intact and the rest of the h-tree looks ok...
hmm... another mystery to be solved...

Hopefully you can solve this mystery to what happened to this charger