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BQ28Z610-R1: 0-V charging issues

Part Number: BQ28Z610-R1
Other Parts Discussed in Thread: BQ28Z610

The customer are using BQ28Z610 and take measurement. If the battery is set as 2V (Vbat+ is 2V) and the adapter plug in, the CHG pin voltage is 3.9V (1.9V higher than the Vbat+).

1.So the customer want to know whether it is this normal?

2. Whether the CHG gate voltage is fixed?  Because this will affect the chose of CHG FET.

3. Is there any description of the hardware 0-V charging circuit?

  • Hello Fabio,

    Does the battery voltage go higher when the adapter is connected?

  • The CHG Mosfet is still off. Because the Vgs is just 1.9V, which is too low. So the battery voltage is still 2V.

    1. Whether the CHG gate voltage is fixed? I know there is a charge pump in the chip?

    2. Is there any description of the hardware 0-V charging circuit?

  • The gauge will connect PACK to CHG with a voltage offset. So the voltage that you measure will follow the charger voltage.

  • Hi Dominik,

    I noticed the Vdsg description. From my understanding,

    1. When the VC2 voltage is below 2.2V, the BQ28Z610 will enable 0V charging circuit. Is it right?

    Where I could find the minimum operation voltage ?

    2. The gauge will connect PACK to CHG with a voltage offset.

    So is there any Estimate formula?  The CHG voltage and PACK voltage will be a linear relationship?

    This is the important project I mentioned in the email. The customer need to pass one 0V charging function test. So they want to know the working principle more clearly.

    Thanks for your help.

  • #1: This means that the gauge isn't powered up by the cell (VCC min). It'll internally connect PACK via diodes to the CHG FET gate, enabling a small ZV charging current through the DSG FET body diode (the DSG FET is off) and the CHG FET.

    #2: CHG follows PACK with a constant offset.