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BQ76PL455A: Fault_n can not output low when OV and UV occur

Miles Li1
Intellectual 1640 points
Part Number: BQ76PL455A

Hi ,

Customer used bq76PL455A 600V battery pack , and fault_n cannot not output low while register cannot also be read when OV/UV is triggered. Could you explain how to configure so that the OV/UV can be triggered automatically?

Thanks!

  • 0
    TI__Genius 17440 points

    Hi Miles,

    Can you clarify which OV/UV you are referring to? Are you referring to the cell OV/UV or the window comparator OV/UV?

    Best Regards,

  • 0 in reply to Kristin Jones93
    TI__Intellectual 1640 points

    Hi Jones,

    Yes. According to customer description, he need to verify whether the cell OV/UV function. However, fault_n cannot output low as well as he reads nothing from the register whenever he trigger the OV/UV condition he sets. 

    Could you help to provide suggestion about this issue? Do customers miss some operation procedure? 

    Wish to get your reply as soon as possible. Thanks!

  • 0 in reply to Kristin Jones93
    TI__Intellectual 1640 points

    Hi Jones,

    Do you have any update about my questions? Thanks!

  • 0 in reply to Miles Li1
    TI__Genius 9401 points

    Hi Miles, 

    To use CELL_OV and CELL_UV they need to set the desired OV threshold voltage in register CELL_OV (0x90-0x91) and the desired UV threshold voltage in register CELL_UV (0x8E, 0x8F). If all 16 channels are used then they need to make sure that all 16 channels are enabled in register NCHAN (0x0D). After that, if they increase the voltage above the OV threshold configured, then the fault for the corresponding cell will trigger in register FAULT_OV (0x56-0x57). Similarly, if they decrease the voltage below the UV threshold configured then the fault for the corresponding cell will trigger in register FAULT_UV (0x54-0x55). 

    Best regards,

    Leslie

  • 0 in reply to Leslie Marquez
    TI__Intellectual 1640 points

    Hi Leslie,

    First of all, thanks for your reply. However, it seems that the solution you suggest cannot influence the fault_N output. Do you have other idea? Thanks!

  • 0 in reply to Miles Li1
    TI__Genius 17440 points

    Hi Miles,

    The CELL_OV and CELL_UV faults will cause FAULT_N to assert (see section 7.3.12.3.1 of the datasheet). Can you clarify how the customer is testing this behavior? Also please keep in mind that FAULT_N is active low and that if a fault occurs FAULT_N will latch and stay low until the fault is cleared.

    Best Regards,

  • 0 in reply to Kristin Jones93
    TI__Intellectual 1640 points

    Hi Jones,

    I have let the customer to do below actions:

    1. Set the OV/UV value in [COMP_OV] and [COMP_UV];
    2. Set the value of CELL_OV (0x90-0x91)和CELL_UV (0x8E, 0x8F) ;
    3. Select the Vsense channel in [[NCHAN]];
    4. Enable OV/UV in [FO_CTRL];
    5. Enable DEVCONFIG[COMP_CONFIG];

    Once all are set, they would will simulate OV/UV condition in Vsense pin. And the results are that they find FAULT_N cannot output low.

  • 0 in reply to Miles Li1
    TI__Genius 9401 points

    Hi Miles, 

    Before checking the NFAULT pin, please check the FAULT_OV and FAULT_UV registers first. If there is a fault it will be reflected on these registers. Also, please share the CELL_OV, CELL_UV value that the customer is setting on these registers, as well as the actual cell voltage to make it trigger.

    Regards,

    Leslie