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Question of BQ24133 Cell selection pin.

Chee Ho Kar96
Prodigy 90 points
Other Parts Discussed in Thread: BQ24133

Hi TI,


I am using BQ24133 to design a 2Cells and 3Cells charging circuit. I know that the pin 14 "Cell" is using for select cell number.

High for 3Cells, Float for 2Cells. Refer to the following picture, is that possible to use a P MOSFET for select High and Float states?

Many thanks

  • 0
    TI__Expert 3160 points
    Hi,

    Yes, you can select between cell pin settings using external circuitry.

    Best,
    Rachel
  • 0 in reply to Rachel Moore
    Prodigy 90 points

    Thanks for your reply, and I have one more question.


    Refer the BQ24133 datasheet, the IC has two MOSFET to control adepter input current.

    Because for the cost and PCB size limit and I don't need the input current control function, is that possible to replace that circuit by only one diode? And I also remove the ACSET, ACN, ACP circuit. Please see my circuit below:


    Many thanks.

  • 0 in reply to Chee Ho Kar96
    TI__Expert 3160 points

    It's not recommended for higher input voltages, but it's possible to use only Q1.  Q1 controls inrush current and Q2 is a reverse blocking FET.

    Additional comments:

    • ACSET should be pulled high to VREF
    • Add 330 pF cap in parallel to R49
    • Recommend an additional 10uF cap on V_BAT node.  If cost senestive you can change to DNP if performance is okay without.
    • please reference the EVM documentation for recommended schematic and layout

    Best,

    Rachel

  • 0 in reply to Rachel Moore
    Prodigy 90 points

    Thanks for the comments.



    Now I have a PCB that follow the schematic which show in my provided picture,
    already pull ACSET to VREF and ACN/ACP connect to DC15V without the current sense resistor. And the IC pin "STAT" always blinking. I also measure all setting pins voltage are match the requirement.

    So that BQ24133 cannot work well without Q1 and the current sense resistor connect to ACN/ACP?

  • 0 in reply to Chee Ho Kar96
    TI__Expert 3160 points

    Blinking STAT pin indicates a charger is in FAULT mode. Does STAT blink when there is a battery only, no adapter? 

    You can reference Table 3 in the bq24133 datasheet for a full list of fault conditions. 

    Thanks,

    Rachel 

  • 0 in reply to Rachel Moore
    Prodigy 90 points

    Because I didn't connect Battery back to BQ24133, so the blinking only happen when the PCB has adapter. the STAT will blink when battery connect and not connect.

    Refer to your suggestion, I have change my PCB as the below schematic:

    Because of the PCB design, I cannot add "Q1" and "Input current sense R" right now, will it cause the FAULT if ACN/ACP not connect to resistor?

    Many thanks

  • 0 in reply to Chee Ho Kar96
    Prodigy 90 points
    Hi Rachel,

    I forgot to connect the battery NTC pin, after connect it, the circuit work. At least it start charging and the current within limit.
    Thanks for your help.
  • 0 in reply to Chee Ho Kar96
    TI__Expert 3160 points
    Glad your circuit is working now! Please come back if there is anything else I can help you with.

    Best,
    Rachel