nPM1300 LiPo and short protection

[Den Engineer]

Hey, wanted to know a few things regarding npm1300

1. Can it handle short circuit of it's buck/LDO outputs? Or we need to have some sort of protection for each buck.
2. If there is some kind of short protection on the outputs, does it make sense to add overdischarge current protection for LiPo? There is very little chance for short happening between Lipo and npm1300 in our case - most likely lipo holder itself will short OR smth after npm1300 will short - seems that adding extra protection in between lipo and npm1300 would not help.
3. There is overvoltage termination for LiPo, right? So it does not make much sense to add extra overvoltage protection? (besides handling cases of npm1300 failure when it would not respect termination voltage and continue charging).
4. There is no lipo reverse polarity protection and npm1300 would not be able to gracefully handle 1-2 minutes of bat. connected in reverse, (so that needs to be added externally) correct?

Thanks!

[Szabolcs]

Hi Denis,

1. The buck converters have switch current limiter that will limit the output current in case of short circuit. Also, VBUS and battery have programmable current limiters that will limit the current in case LDO/LS is shorted to GND.
2. It is recommended to have a battery pack with integrated PCM (Protection Circuit Module) for protection against overcurrent discharge for safety reasons, but no additional protection between the battery pack and the PMIC is needed. If you are using industrial cells without modules, I recommend adding at least a fuse between the battery and the PMIC.
3. The charger does have programmable termination voltage, but it is recommended to have a PCM with overvoltage protection for safety reasons.
4. Correct, there is no battery reverse current protection, so if that is required from the system point of view that needs to be added externally.

Overall, the PMIC is intended to be used with a battery pack that has integrated PCM. Using bare industrial cells is not recommended.

[Den Engineer]

Got it, thanks!

On 4 tho - will it destroy the PMIC? I did read somewhere on devzone that it will get quite hot, but not sure if it could withstand that kind of abuse let's say 4-5 times with maximum reverse polarity lipo connection time within 1-2 minutes? Or you don't have any data on that (we don't expect ppl to do it often, but just in case it happens we don't want device to be dead ofc.).

[Szabolcs]

The nPM1300 EK datasheet mentions that connecting the battery in reverse polarity causes the device to become very hot. However, we don't have any data regarding the resilience against reverse polarity.

Even if the nPM does survive that for 10-20 seconds, I think 1-2 minutes would be just too much, and the IC would get damaged just due to the overheating itself. (It might even let out the smoke - depending on the power of the battery.)

Maybe if there is overcurrent protection in the battery pack, that would trigger and disconnect in an event of accidental polarity reversal before any damage could be done.

[Den Engineer]

I see. Thanks!

We can't have PCM on the cells since we need coin cells, but seems like overvoltage, reverse polarity and overdischarge is a must so we will add them externally.

[Szabolcs]

Good! I'm glad I could help.

[Den Engineer]

Could you please quickly check if that's looks fine for npm1300? Protection IC is basically DW06 and this NMOS for reverse polarity.

[Szabolcs]

Yes, I think this implementation is good.

[Den Engineer]

Perfect, thanks!