Reverse polarity protection for coin cell?

Hi all,

I want to make my own board that will accept a 3V coin cell (Cr2032) and boost to 3.3V for a low power application.

I would like to use the LTC3525-3.3 to accomplish this, however, I read the datasheet and do not see anything about reverse polarity protection.

I've found some general schematics online using mosfets or diodes to provide reverse polarity protection, but this usually results in a voltage drop. The LTC3525 has a startup voltage as low as 0.85V which is great so that even low batteries should still work and provide long battery life. However, introducing the typical reverse polarity protection circuits will result in the voltage drop penalty. This reduces the amount of usable battery life available.

Is there some kind of reverse protection circuit without said voltage drop?

Thanks!

doublec4: I want to make my own board that will accept a 3V coin cell (Cr2032) and boost to 3.3V for a low power application. I would like to use the LTC3525-3.3 to accomplish this, however, I read the datasheet and do not see anything about reverse polarity protection.

Why do you need reverse voltage protection. The design of a CR2032 button battery holder prevents powering the circuit with a reverse voltage. Leo..

Some battery holders are designed with one contact on the circumference of the cell and one contact on the centre of one of the cells faces. Only a correctly inserted cell will apply a voltage across the output terminals.

Using one of these should solve your problem (as long as you wire it the right way round in the first place).

You beat me to it, Wawa.

doublec4: I want to make my own board that will accept a 3V coin cell (Cr2032) snip provide reverse polarity protection snip

You could 'crowbar'-protect the device with a schottky diode across the battery, guessing the short-circuit current from a CR2032 can't be much ?

Yours, TonyWilk

TonyWilk: You could 'crowbar'-protect the device with a schottky diode across the battery, guessing the short-circuit current from a CR2032 can't be much ?

Yours, TonyWilk

Short circuiting a Lithium cell isn't to be recommended.

http://batteryuniversity.com/learn/archive/lithium_ion_safety_concerns

As others have mentioned, it’s unnecessary with a coin cell unless you have a terrible holder (almost all of the ones - maybe all of them - that I’ve seen don’t make the connection if the battery is in backwards).

That said, as an academic exercise, the classic way to do this is with a FET with the gate tied to the opposite power rail, drain to input, source to load.

Thanks guys. Embarrassed to say I didn't even consider that the holder should be designed accordingly. However, the one I have on hand looks like this:

|500x500

and it would appear that it would be possible to install backwards momentarily. If the battery is installed upside down partially, the contacts on the clip make contact with the center (-) portion of the battery and because it is not fully inserted, it does not touch the sides (+) at the same time.

I'll be sure to find a better holder instead!