MP2722: Behavior without battery connected/battery connected after USB

Battery Management
1

Hello!

I am planning to use the MP2722 for a powerbank/battery charger device with a user accessible battery bay. So it is possible that the users will plug the PCB into a USB port before inserting a battery, or remove the battery before unplugging.

How exactly will the chip behave in this case? Will it still apply power to SYS, as SYS will be powering a microcontroller to control the PCB, that needs to be running at any given time (battery only and no USB, USB only and no battery).

If it is plugged in without a battery connected, will it just set the BATT_MISSING flag, but still power SYS? Will this flag be automatically cleared after plugging in a battery (or can the MCU clear it), or does the chip need a power/reset cycle after?

Oh, and does the chip include any kind of reverse polarity protection (against wrongly connected batteries)? I currently added one myself, but if I can omit that it will save me PCB estate and series resistance.

Kind regards,
Moritz

2

Hi Moritz,

This part does have power path management to prioritize SYS using input source/battery. So if you remove Vin, the Vsys should still be provided as long as battery is there and vice versa.
Yes if battery is missing, the interrupt will occur. From my understanding, the batt missing register will be 1 and go to 0 when battery is inserted. I believe SYS should still be there if input source is there as SYS is prioritized.

You can test this on our evaluation board as well.

This does not have reverse polarity protection, so this could damage the part. Most battery packs have the reverse polarity protection circuit inside.

Best Regards,
Yu

3

Hi Yu,

Thank you very much! That’s valuable information.

I’m considering buying the devkit - since this is a hobbyist project that may or may not end up in a larger production batch, I’m debating if it is worth the investment so far. While the devkit itself is surprisingly economic, the whole eval kit with the i2c tool is rather expensive for a private customer. Maybe I will go for the bare devkit and a cheap Arduino for testing.

Thanks for confirming my expectations about the reverse polarity protection. The board will be used with cylindrical unprotected cells, but I placed a RVP on the PCB already, so that is fine.

Have a nice day and thank you again for your help,
Moritz