Is there no Battery UV-Protection in MP2672A?

Battery Management
1

Hi,

we are searching for a 2-Cell LiIon Battery Management System.
The BMS should be part of a handheld, battery powered Test&Measurement device.
As such it is required that there is a undervoltage protection/shut-down to prevent the battery cells from beeing depleted fully.
We came across the MP2672A which seems to have all functionality apart from a battery protection as the batteries seem to remain connected to the load via Q3 till a 5V supply voltage is connected to Vin again and recharges.
How can we protect the batteries from beeing depleted fully?
Are there other BMS devices from MPS that monitor and protect the batteries, or do we have to design a dedicated protection circuit, that cuts the connection to the BMS/load?

thanks in advance
Chris

2

Hi Chris,

Are you specifically looking for protection devices or are you looking for something to charge your batteries as well? The main function of the MP2672A is to charge your batteries, so I wanted to make sure you have chosen the right device here. Can you tell me a little bit more about your system requirements including input voltage, charge voltage, charge current and if power path is necessary? I will look into the BMS side of things for you in the meantime.

Thanks,
Brendan Schoemehl
Field Applications Engineer
Monolithic Power Systems | MPS Now

3

Hi,

the main requirement is to charge the batteries.
But since it is a handheld device the charger will be a integrated subassembly which will not be connected to a external 5V supply (or to USB) for most of the time … certainly not when the device is in actual measurement use.
The MP2672 features the SYS-output where a load may be connected to.
The datasheet states that if Vin is not high enough Q3 will be switched on, thereby connecting the battery to the load.
The datasheet also states that there is a overvoltage protection for the batteries.
But I can´t find a UV lockout, that inactivates Q3, or decouples the load from the batteries, nor seems an dedicated UV-output to exist.
As I understand it, the batteries will be drained completely in the case that You use the device and ´forget´ to disconnect the load at the SYS-pin and no 5V supply is connected.
A case that easily may occur with handheld devices.
A simple hardware On/OFF switch between output ´SYS´ and the load would cut the line between charger and circuitry, but won´t help when forgotten to be switched off.
So the question is:
Is there a means to protect the batteries against complete drainage when Vin is not present?
If No, are there other charger ICs from MPS that have that functionality integrated, or are there ICs that I can add to the MP2672A to achieve Battery UV-protection?

thank You in advance
Chris

4

Hi Chris,

Thank you for expanding on this some more for me. I’m reviewing, I’ll let you know my thoughts soon.

Thanks,
Brendan

5

Hi Chris,

Still looking into this for you, should hopefully have answers for you by the end of the week.

Thanks,
Brendan

6

Chris,

You are correct, there is no under voltage lockout specifically for the battery on this device. You would completely deplete the battery if you leave the discharge on. However, there is a preconditioning charge for a deeply depleted battery on this device. This essentially pre-charges the device in a safe way before the device starts the normal charge cycle. This preserves the battery health better than no protection at all, but note there is no shutoff like how you are asking.

If you need a device with battery UVLO, take a look at the MP2762A. Note that it does not have the cell balancing capabilities of the MP2672A. What do you think of this device?

Thanks,
Brendan