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BQ25756E: Behaviour without a Battery

Part Number: BQ25756E
Other Parts Discussed in Thread: BQ25756, BQ25570,

Tool/software:

My device should be able to operate even when there is no battery connected:

What happens when I apply an Input voltage without a battery? Will the BQ25756 turn its Buck-Boost-Converter on and supply an output voltage?

I know the BQ25570 and others with a Direct-Power-Path products exist, however this is not what I want as those don't regulate the input voltage (My input voltage varies, as it's provided by USB PD or an Auxiliary Input. I don't want the subsequent power circuitry to be subjected to this wide input range (approx 5V-36V) and would like to regulate it first (to around 4S, 16.8V) ). I was hoping the BQ25756 could both regulate an Input Voltage when no battery is present and charge the battery when it's connected.

Is this possible with a single BQ25756 or should I pre-regulate my input voltage and then use a Direct-Power-Path charger?

  • Hello Robin,

    I would recommend using a DC/DC converter and then using a direct power path charger.

    The BQ25756E can regulate a steady DC-DC output though. You'll need to set EN_TERM=0, EN_PRECHG=0, and you'll need to make sure the system load doesn't exceed charge current set. You'll also want to make sure your battery can handle being hot plugged into the circuit.

    Best Regards,
    Ethan Galloway