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BQ24172: Input current limit value Idpm

Kuramochi Tadahiko
Guru 28715 points
Part Number: BQ24172

Hi,

My customer is considering the failure mode of the BQ24172.

What ampere is the input current limit value when the R5 is opened on following schematic?

Best Regards,

Kuramochi

  • 0
    TI__Genius 10640 points

    Hi Kuramochi,

    Input current limit setting is shown in datasheet"9.3.4 Input Current Regulation".

    If customer still use 10 mohm as RAC and open R5(ACSET pulls up to Vref), input current limit will be set higher than normal operation(won't reach IDPM). We recommend customer follow reference design to set input current limit by voltage divider.

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    Guru 28715 points

    Hi Ann-san,

    Thank you for your help.
    We're recognizing your comment and considering the failure mode.

    IDPM has no maximum limit.
    Is it correct?

    Best Regards,
    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    TI__Genius 10640 points

    Hi Kuramochi,

    There is a ACP-ACN maximum setting shown below.

    If we use 10mohm as RAC, the input current limit can be set at 20A. it depends on different RAC. But there isn't a common situation to use this really high current value as input current limit.

    I've checked with EVM(input current can't be higher than 8A), If V_ACSET get higher, input current limit will get higher but not over 8A because of the EVM board limitation.

    Best regards,

    Ann Lien

    Best regards,

    Ann Lien

  • 0 in reply to Ann_Lien
    Guru 28715 points
    Ann-san,

    Thank you for your support.

    >input current limit will get higher but not over 8A because of the EVM board limitation.

    What is this 8A limit by?
    As result, does IDPM has no maximum limit?

    Best Regards,
    Kuramochi
  • 0 in reply to Kuramochi Tadahiko
    TI__Genius 10640 points

    Hi Kuramochi,

    The 8A limitation is the EVM input current maximum, you can see the spec. in EVM user guide "1.5 Recommend Operating Condition".

    As I mentioned in the last reply, bq24172 has ACP-ACN maximum, it can operate normal IDPM function in this range. We cannot ensure the condition over this range. In your case, ACSET is pulled up to VREF and the IDPM value will be 16.5A(RAC=10mohm). But I can not simulate the condition due to the input current limit 8A limitation. Do you have bq24172 EVM board? We recommend you use different RAC and V_ACSET to check the IDPM function.

    Best regards,

    Ann Lien