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BQ2970: How to turn on BQ2970?

Paul Yeh
Genius 13625 points
Part Number: BQ2970

Hi Team,

My customer asked one question about when COUT/DOUT will pull high to turn on external FET.

The condition is customer will plug in battery at first and battery voltage is around 3.4V, then they will apply one power supply and slowly increase output voltage.

So my customer 's question is what voltage level BQ2970 will turn on FET?

Please advise.

Below is testing fixture.

Thanks

Thanks

  • 0
    TI__Guru* 77343 points

    Hi Paul,

    The FETs should be powered on unless a fault condition is detected. There are five different types of faults that can turn off the CHG or DSG FETs: OVP, UVP, OCC, OCD, and SCP. OVP and OCC faults will both turn off the CHG FET, UVP, OCD, and SCP faults will turn off the DSG FET.

    Are they asking what voltage needs to be applied by a charger to turn the FET back on after a fault has occurred? The voltages thresholds are dependent on the specific part number as defined in the datasheet table and the hysterisis defined in the datasheet.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Genius 13625 points

    Matt,

    Customer is designing BQ29700.

    And yes, I am asking what voltage needs to be applied by a charger to turn the FET? see below datasheet's description.

    And could you also guide me where is the The voltages thresholds because I didn't find, sorry.

    Thanks

  • 0 in reply to Paul Yeh
    TI__Guru* 77343 points

    Hi Paul,

    The voltage on the PACK+ / PACK- pins must be high enough for there to be at least 1.3V between V- and BAT pins. You can look at this as a voltage divider where there is 330 between PACK+ and BAT, RV-D is between BAT and V- in this state which is somewhere between 100k and 550k ohms, and there is 3.3k between V- and PACK-.

    I calculate that around 1.35V, DOUT should turn on. I think 1.7V is safe to assume DOUT will be on under all conditions.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    TI__Genius 13625 points

    Matt,

    Thanks