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BQ24735 Low Voltage Cutout.

Andrew Price
Prodigy 130 points
Other Parts Discussed in Thread: BQ24735

I am developing a design for a Lipo Charger for an embedded device and I am using a BQ24735 EVM to get the design started.

During testing I used a digital load to  discharge the battery at 500mA and I was expecting the System voltage to be shut off once the Battery voltage passed below 8.943V. Which is 70.97% of the charge voltage (12.6V)


I discovered that the Battery Voltage went past this number and kept on dropping until I terminated the test.

Am I correct in saying this device does not support low battery voltage cutout? Given the inherent danger with lipos being over discharged, how might I implement a low voltage cutout on the battery?

Any suggestions appreciated

A

  • 0
    TI__Guru 56650 points

    Power MosFET has a body diode. Even, the charger turns off BATFET, the battery current can still go through the body diode to system.

    A fuel gauge IC can control a pair back to back FETs (one charge FET and one discharge FET). After battery voltage is lower than the setting threshold, the discharge FET could be turned off and support the low battery voltage cutoff.

    Please post a new post on fuel gauge forum to get the latest fuel gauge part number.