• State TI Thinks Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 354 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25790: How to deal with unused TS pin

Charles (KAT) Zhang
Intellectual 1595 points
Part Number: BQ25790

Tool/software:

Dear team,

My customer met an issue with unused TS pin.  They want to config TS_IGNORE as 1, however, since the TS_IGNORE is 0 by fault, under AC only condition (no battery), the charger is wake before the MCU, and with connections below they found Vsys and VBAT even reaches to 23.5V. so they want to know how to deal with the unused TS pin， should they make it float?

6746.sch.zip

【Test results】:

condition: default regs setup, no load connected. no battery connected, AC connected

with R0550 populated, Vsys and Vbat reaches 23.5V (Customer want to know why)

with R0550 not populated, Vsys is 7.2V, VBat no output

Thank you

Charles

  • 0
    TI__Intellectual 1110 points

    Hi Charles, 

    No, they should not make TS float. If they are wanting to ignore TS without setting TS_IGNORE = 1, then a resistor divider across REGN is needed to TS hardware disable. This is what the EVM uses for testing:

    For a TS normal: 5.23kΩ between REGN and TS and 30.1kΩ || 10.0kΩ = 7.5 kΩ between TS and AGND. You want TS to be ~55% of REGN.

    If charge is disabled and there is no battery then TS should be irrelevant.

    Regards,

    Jared Baxter

  • 0
    Prodigy 30 points

    Hi Jared,
    Will the voltage of Vsys continue to rise until Vsys is damaged when batp and batn are grounded or floated?

  • 0 in reply to zheng liu
    TI__Intellectual 1110 points

    Hi Zheng,

    How are BATP and BATN connected to BAT? The feedback loop does not look complete from the schematic, which in boost will cause overshoot. I recommend BATN be tied close to IC ground.

    Regards,

    Jared Baxter

  • 0
    Prodigy 30 points

    Hi Jared,

    So you mean that BATP and BATN cannot be grounded or floated, BATP needs to be connected to VBAT, and BATN needs to be connected to GND?

    Also, I would like to know how much voltage VSYS will rise to if BATP and BATN are grounded, and is there a risk of damaging the chip?

    Thanks!

  • 0 in reply to zheng liu
    TI__Intellectual 1110 points

    Hi Zheng, 

    zheng liu said:
    Also, I would like to know how much voltage VSYS will rise to if BATP and BATN are grounded, and is there a risk of damaging the chip?

    I was not able to reproduce VSYS rising as was described. However, use of BATP and BATN outside of the recommended operating conditions can cause IC damage.

    zheng liu said:
    So you mean that BATP and BATN cannot be grounded or floated, BATP needs to be connected to VBAT, and BATN needs to be connected to GND?

    Correct, BATP and BATN are used for remote sense of battery. However, if not connected to the battery terminals, BATP should be connected to BAT. If a ship FET is used, BATP should be connected to the drain of the ship FET. BATN should be connected to ground.

    Regards,

    Jared Baxter

  • 0
    Prodigy 30 points

    Hi Jared,

    Another question, I would like to know what is the leakage current of BATP&BATN when BQ25790 is charged and not charged? Thanks!  

  • 0 in reply to zheng liu
    TI__Intellectual 1110 points

    Hi Zheng,

    Quiescent currents from the datasheet:

    Regards,

    Jared Baxter