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BQ25703A: PROCHOT Triggering - Can't get a trigger for battery removal

greg rise
Prodigy 95 points
Part Number: BQ25703A


Using the TI EVM bq25703AEVM-732 board with default setup I can not get the PROCHOT to trigger when the battery is removed.

Is there a trick or special setup required to get this trigger? Maybe there is a poorly named register need to be set in order to accomplish this?

I will include the register settings I have been using with no luck.

Additionally does TI have a recommenced power up register sequence and corresponding power down register sequence?

From datasheet page 25,

The PROCHOT triggering events include:
• ICRIT: adapter peak current, as 110% of ILIM2
• INOM: adapter average current (110% of input current limit)
• IDCHG: battery discharge current
• VSYS: system voltage on VSYS
• Adapter Removal: upon adapter removal (CHRG_OK pin HIGH to LOW)
• Battery Removal: upon battery removal (CELL_BATPRESZ pin goes LOW)
• CMPOUT: Independent comparator output (CMPOUT pin HIGH to LOW)

my register settings.

  • 0
    TI__Guru 56650 points
    Do you pull the CELL_BATPRESZ pin from high to low (falling edge)? Would you show the /PROCHOT and CELL_BATPRESZ pin waveform?
  • 0 in reply to Wang5577
    Prodigy 95 points
    Hi Wang5577

    I think I ended up answering my own question. From what I can tell it looks like the CELL_BATPRES pin should actually be hooked up to VBAT via an appropriate voltage divider and not via VDDA or any other voltage generated by the IC. This is misleading as when you look at the datasheet and eval board they guide you in the wrong path and don’t give a clear description on how to wire CELL_BATPRES pin for correct part operation.
    I would like to suggest TI update the datasheet so it is clear on the intended connection and confirm my assumption above.

    I have a handful of other odd things that I would like to talk through with an expert on this IC to understand correct/intended usage. Is there a way to arrange this or must all question go through these forums?

    Thank you,
    Greg
  • 0 in reply to greg rise
    Prodigy 95 points
    I did some calculations and hooked up a voltage divider to VBAT and tried out my theory... it did not work. This leads me to believe that the only way this IC can detect a battery removal is via an external switch that would pull CELL_BATPRES low. Hopefully there is some other way that this IC can detect a battery removal. Please advise.
  • 0 in reply to greg rise
    TI__Guru 56650 points
    bq25703a doesn’t monitor battery charging voltage and current to do the battery removal detection. Bq25703A will wait for the host or the system hardware to pull down CELL_BATPRESZ pin to know the battery is removed.
    Host or system hardware pulling CELL_BATPRESZ low generates one-shot falling edge. That can trigger BATPRES PROCHOT.
  • 0 in reply to Wang5577
    Prodigy 95 points
    Hi Wang Li21,

    Please have the datasheet clearly updated to indicate this requirement for proper part operation. The datasheet reads as if the IC is doing the battery removal detection and that the host/system hardware is not required to pull CELL_BATPRES low.
  • 0 in reply to greg rise
    TI__Guru 56650 points
    The host/system needs to pull CELL_BATPRESZ low to let bq25703A know the battery removal.
    Please order an EVM to verify this function.