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BQ25703A: CELL_BATPREZ dual functionality issue

jorgen.olsen
Prodigy 195 points
Part Number: BQ25703A

I use a 2s configuration which is configured through the "CELL_BATPREZ" pin. This pin has according to the datasheet also the function to detect a removed battery by forcing the voltage to a maximum of 15% of the VDDA(or REGN). I can not get the pin to respond accordingly? I use the EVM to ensure that my design will work in the future and this could save a troublesome mechanical switch.

Jørgen Olsen

  • 0
    TI__Guru 56650 points

    "I can not get the pin to respond accordingly?" Could you give more detail about it? What do you want to see? And, what test result do you get from the EVM?

  • 0 in reply to Wang5577
    Prodigy 195 points

    Hi Wang5577

    According to the datasheet this pin should have a dual functionality: as input:setting the number of cells, as output: pulled to max 15% of V(REGN) if the battery is removed.

    So I expected the pin to drop to a max of 0.9V when I remove the battery. I know that I can use the HOTPROC pin for the same purpose but if I could use the

    other as an immidiate interrupt signal without making a lot of I2C communication, then this would be welcomed.

    Regards

    Jørgen

  • 0 in reply to jorgen.olsen
    TI__Guru 56650 points

    CELL_BATPRES pin is an input pin. On the datasheet, Page 4, pin functions: it shows an input pin in the "i/o" column.

    Where do you find it is an output pin? I will submit the update to correct it if you find it is an output pin.

  • 0 in reply to Wang5577
    Prodigy 195 points
    On the same page the text says: Battery cell selection pin for 1–4 cell battery setting. CELL_BATPRESZ pin is biased from
    VDDA. CELL_BATPRESZ pin also sets SYSOVP threshold to 5 V for 1-cell, 12 V for 2-cell ,
    18.5 V for 3-cell, and 19.5 for 4-cell. CELL_BATPRESZ pin is pulled below
    VCELL_BATPRESZ_FALL to indicate battery removal.
  • 0 in reply to jorgen.olsen
    TI__Guru 56650 points
    "CELL_BATPRESZ pin is pulled below VCELL_BATPRESZ_FALL to indicate battery removal." This talks about an external circuit needs to pull down CELL_BATPRESZ pin to let bq25703A to know the battery removal.