Schematic problem - It gets hot and smells like burning (lemmy.ca)

submitted 1 month ago by Shadow@lemmy.ca to c/askelectronics@discuss.tchncs.de

8 comments fedilink hide all child comments

I've been messing around with circuits my entire life but this design was time sensitive and I've never done my own PCB designs before, so I hired someone to put this together. After getting some test boards, when I plug them in the charger chip gets very hot and smells like burning....

Circuit is just a simple li-ion usb charger and a switch. I've gone through the datasheet for the bq25302 more times than I can count and I'm missing something obvious here. Using it just for delivering power seems to work fine, the problem is only when charging.

I do see R6 + R7 off TS don't have the recommended 10k values, but I don't feel like that would cause what I'm seeing. This is being connected to a 21700 lipo.

Someone mind lending me their eyes please?

bq25302 datasheet - https://www.ti.com/lit/ds/symlink/bq25302.pdf

top 8 comments

sorted by: hot top controversial new old

[-] AnarchoSnowPlow@midwest.social 4 points 1 month ago

I could be wrong, but I did finish a degree in EE even if I just do software now. But here's my quick take on it.

Probably because you're driving voltage on STAT from REGN.

STAT should have a current limiting resistor on it, go through your led, then ground.

REGN should have a 2.2uf cap between the pin and ground according to the datasheet.

[-] Shadow@lemmy.ca 2 points 1 month ago

STAT should have a current limiting resistor on it, go through your led, then ground.

That would make sense, but page 21 of the datasheet with a typical application shows it going to REGN.

If it's missing the cap on REGN though, that would probably fuck this all up? I must admit I'm not good at understanding when/where caps are applied.

[-] cmnybo@discuss.tchncs.de 3 points 1 month ago

There should be a capacitor between REGN and ground and BAT and ground.

[-] Shadow@lemmy.ca 1 points 1 month ago

Oooh, thanks.

Stupid schematic question for a second, when looking at this:

If the "REGN" above the LED there is just referring to the REGN pin right below, why doesn't the line just go back down to the pin? Is this just a style thing, or does it mean something functionally different?

[-] cmnybo@discuss.tchncs.de 3 points 1 month ago

It means the same thing. I would have just drawn a line since they are right next to each other.

[-] Shadow@lemmy.ca 1 points 1 month ago

Thanks!

[-] Landslide7648@discuss.tchncs.de 1 points 1 month ago

If you don’t mind me asking: what is this for? Is it a hobby? I have no idea if any of this, just somehow came across your post

[-] Shadow@lemmy.ca 1 points 1 month ago

Long term hobby that I'm trying to now turn into a small business / online store.

this post was submitted on 12 Sep 2024

18 points (95.0% liked)

Ask Electronics

3173 readers

2 users here now

For questions about component-level electronic circuits, tools and equipment.

Rules

1: Be nice.

2: Be on-topic (eg: Electronic, not electrical).

3: No commercial stuff, buying, selling or valuations.

4: Be safe.

founded 1 year ago

MODERATORS

DavideAndrea@discuss.tchncs.de

linker3000@discuss.tchncs.de