• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 698 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.

BQ24296M: Thermistor and ILIM Questions

Matt Staniszewski
Intellectual 360 points
Part Number: BQ24296M
Other Parts Discussed in Thread: BQ25606

Hi,

I have a few design questions related to the BQ24296M:

1) Our LiPo battery does not have a thermistor.  How do you disable the TS signal?

2) In regards to PSEL and ILIM, does the charger use the lower of the two current limits?  For example, if PSEL = 0 (adapter, 3A) and ILIM is set for 2A, will the charger max out at 2A?

Best,

Matt

  • 0
    TI__Guru**** 166626 points
    Hi Matt,

    Regarding 1, you can add a resistor divider from REGN with the same value resistors, e.g. 10k/10k to convince the TS pin that the battery is at 25C.

    Regarding 2, yes. ILIM is a clamp that prevents the input current from going above the resistor selected value, regardless of PSEL or IINDPM register settings.

    Regards,
    Jeff
  • 0 in reply to Jeff F
    Intellectual 360 points

    Hi Jeff,

    Thanks for the help on those.  I've finished my draft schematic, see attached.  Can I NC the PG, STAT, I2C and INT pins if not in use?

    Let me know if everything looks OK.

    Best,

    Matt

  • 0 in reply to Matt Staniszewski
    TI__Guru**** 166626 points

    Matt,

    Yes, you can leave those pins NC. However, without STAT, PG, INT, you will not be notified of events, such as faults occurring. Also, without I2C connection, you cannot directly change charge current (you must use the default value) and, with /CE grounded, you have no way to reset the IC in the event that the safety timer expires, for example. Just curious why you chose this part and not the standalone BQ25606?

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Intellectual 360 points
    Hi Jeff,

    Yes, I understand that we lose some debug capability. I have added test points to all NC pins and a debug header for I2C. We are relying on the switching of the ILIM resistor values to set the charge current as this is a dumb device with no MCU / host control.

    The BQ25606 looks like a good part too, it was on my list for possibilities. Perhaps for the next rev we can switch.

    For a standalone operation, would you recommend the CE# signal be connector to a button?

    Matt
  • 0 in reply to Matt Staniszewski
    TI__Guru**** 166626 points
    Matt,

    STAT, INT and PG are open drain so if you want full functionality, you will have to add pull up resistors to SYS.

    Yes. I recommend adding the ability to pull /CE high either with a button or jumper.

    Regards,
    Jeff
  • 0 in reply to Jeff F
    Intellectual 360 points
    Thanks Jeff, I'll take those changes into account.
    Matt