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BQ24074: Undervoltage Protection?

Part Number: BQ24074

Dear TI,

In a close reading of the datasheet for part BQ24074, it is not obvious to me what the state of the chip is when the power IN is disconnected and the battery voltage is also below 3V (Vlowv), so I am unsure if I need an added undervoltage protection circuit to keep the battery from discharging too far and breaking. I want to make sure Vbat is disconnected from OUT if Vbat drops below 3V, naturally with some hysteresis to avoid flickering undefined power states.

I see no reference to this in the text, but seeing as how the chip has a 3.0V reference and many comparators inside is this just a feature that's not noted?

Would you recommend a different chip for permanently installed batteries?

I'd hate to duplicate functionality that is already present. I am just confused as I see no mention of it in the datasheet but it's clearly required functionality to include shutting off battery use if the battery is dead.

Brian

  • You need a BUVLO circuit to protect that device from discharging. The BQ24074 does not have this function.

    When VBAT drops below 3V without VIN, VOUT will continue to be powered by the battery. 

    What is your charge current?

  • Thanks, I will add one then. Right now I am using LT6703-3 as a self-powered comparator with hysteresis on the battery voltage with the output used to disable the downstream regulator enable pins. It is a little expensive, unfortunately, but has worked well for me.

    I have an inlet current rating of 500mA and a charge current of 200mA. I did find the application note that explained how to select the resistor values.

    Brian