BQ25703A: VBAT_UVLO for 4-Cell

Mark Philip Felipe

Part Number: BQ25703A

Hi Team,

In the datasheet section called Battery Under-Voltage Lockout Comparator, it seems to say that the battery FET (Q5, driven by the CMC's BATDRV pin), will be driven open if VBAT falls below 2.4V (typical). This is fine for a single cell. But for 4 cells, we need the FET to open if VBat falls below 2.4V * 4 = 9.6V. We are using 4 QB18650 3.7V 3000mA batteries connected in series and a battery must not discharge below 3V

We don't see anything in the datasheet that explains if that voltage is multiplied by the number of cells indicated by the cell configuration. My question is what is the VBAT_UVLO for 4 cells?

Thank you,

-Mark

over 2 years ago

0 Pengzhao Zhu over 2 years ago

TI__Genius 11385 points

Hi Mark,

Thanks for reaching out.

Actually there is nothing to prevent the battery to discharge with our charger alone. As you can see, even if the MOSFET is turned off, the battery will discharge through the body diode of the MOSFET.

Customer typically have separate protection circuitry on their battery pack to prevent the cell voltage from dropping too low.

TI has a good portfolio of those ICs as well.

https://www.ti.com/power-management/battery-management/protectors/overview.html

Thanks and I hope this helps,

Regards,

Peng

*If my answer solves your question, please press "This Resolved My Issue" on the thread.

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BQ25703A: VBAT_UVLO for 4-Cell