Battery protection circuitry for nRF51 (applicable to other nRF products, too)

[Marc Nicholas]

Hi,

We currently (no pun intended!) don't have any battery protection circuitry for reverse polarity designed into our prototypes. Our device is powered from a CR2450 coin cell.

We're using the DC-DC charge pump mode on the nRF51, so using an external LDO with protection doesn't make much sense.

Using diodes obviously results in voltage drop and some current leakage -- both are undesirable. Even Schottky diodes don't really cut it.

There's the virtual ground trick with MOSFETs that would meet the design criteria (low leakage, no voltage drop), but I've also not blown up nRF51s with temporary reverse polarity :p

So my question is: what's everyone doing for battery protection?

Cheers,

-m

[Carles]

Hi there,

I just asked internally and for our own reference designs we don't usually add any specific battery protection other than sometimes adding diodes with low forward voltage drop.

However take this information with a grain of salt: our PCBs are not finished products, they are just designs used to help customers.

Carles

[Marc Nicholas]

Thanks, Carles....this seems in line with my experiences. I suspect the relatively high ESR of a coin cell helps to not release "magic blue smoke" :)

[techpunk]

I am in the same boat and contemplating using MOSFETs for reverse battery protection. N MOSFET www.sipusemi.com/.../si2312ds.pdf P MOSFET www.vishay.com/.../72024.pdf

I wonder what kind of reverse battery protection do coin cell operated reference designs use.

[Michael Dietz]

seems like alot of the battery holders for coin cell have reverse polarity protection 'built in'. i think the case with many holders and coin cell batterys prevents contact from being made on the ground side if it is put in the wrong way. not sure if this is standard or not but worth a double check.

[awneil]

Yes, a battery holder which prevents reverse insertion by design is definitely the way to go - See this article: www.embedded.com/.../Reverse-battery-protection

And, no - not all battery holders do this.