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BQ24610: When Rsns between ACP and ACN is open

Hirotsugu Kobayashi
Mastermind 9540 points
Part Number: BQ24610

Hi, team.

When I removed the sense resistor between ACP and ACN of this device, it burned out.

Will it burn out if the potential difference between ACP and ACN exceeds the rating?
Which internal circuit do you think is damaged?
Is there a protection circuit on the ACP and ACN input terminals?

Best Regards,

  • 0
    TI__Genius 10385 points

    Hirotsugu-san,

    Will it burn out if the potential difference between ACP and ACN exceeds the rating?

    Yes, this violates the absolute maximum voltage rating of ACP - ACN.

    Which internal circuit do you think is damaged?

    It is difficult to know for sure but the PWM logic for the HIDRV and LODRV is most likely damaged based on the functional block diagram. In short, the IC is damaged beyond usability when the abs max rating is violated.

    Is there a protection circuit on the ACP and ACN input terminals?

    Not explicitly. If you plan on not using a sense resistor in your application ACN and ACP can be configured as shown in Figure 24 of the datasheet. This configuration will disable DPM.

    I hope this resolves your issue,

    Ricardo

  • 0 in reply to Ricardo
    Mastermind 9540 points

    Hi, Ricardo.

    ACP and ACN are terminals that measure the input current, so if Rsns is open,

    I think that the input current will be limited and the charging operation will stop, but it burned out.

    The maximum rating between ACP and ACN is 0.5V, is there a bidirectional diode?

    If so, the diode is probably damaged.

    Best Regards,

  • 0 in reply to Hirotsugu Kobayashi
    TI__Genius 10385 points

    Hirotsugu-san,

    It is impossible to know for certain what is damaged in the IC from an external perspective.

    As you have said ACN and ACP are used to sense the input current and are not meant to stop charging operation. If you wish to stop the charging operation please drive the CE pin appropriately.

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Mastermind 9540 points

    Ricardo-san,

    I would like to put a diode in both directions between ACP and ACN to protect it, are there any concerns?

    Best Regards,

  • 0 in reply to Hirotsugu Kobayashi
    TI__Mastermind 24075 points

    Hi Hirotsugu-san,

       I am confused why you are removing the sense resistor between ACP and ACN at all? Input current set point is set based off of the value of the sense resistor between ACP and ACN, along with the voltage on ACSET, and regulated based off of the differential voltage sensed between ACP and ACN. This part already has an input current regulation loop to regulate input current, and on top of that the sense resistor is in the path of the whole input trace. How can you have charging if this resistor is open?

  • 0 in reply to Kedar Manishankar
    Mastermind 9540 points

    Kedar-san,

    We are verifying the reliability when an abnormality occurs in peripheral parts.
    I am considering how to protect the IC because it burned out in the open test of Rsns.

    Best Regards,

  • 0 in reply to Hirotsugu Kobayashi
    TI__Mastermind 24075 points

    Hi Hirotsugu-san,

       I would test using a schottky diode or making sure the fwd voltage drop of the diode is less than 500mV to avoid exceeding the abs max of the ACP-ACN difference voltage. You will have to verify that it doesn't affect the input current regulation feature during normal operation as well.