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BQ79606A-Q1: Base Device's (1 base+ 5 stack) NFAULT Pin Not Response Issue

Stanley Dai
Expert 5810 points
Part Number: BQ79606A-Q1

Hi Team,

My customer is using six BQ79606 (1 base + 5 stack) and one MCU as host to manage 36 cells of Li-Ion. But they encounter an issue that NFAULT pin of base device not respond OV fault. Below is the detailed description of issue background. Can you please provide some ideas to help us close this issue? It will be appreciated to provide some programming procedure material for customer one by one checking. Many thanks.

Below are the issue summary:

  1. When testing base one's OV protection function, the base BQ79606’s NFAULT will respond and show active-low signal. And the second stack one can also read OV alarming signal through daisy chain fault tone. This is normal.
  2. But when testing second stack one's OV protection function, the base device can receive fault tone signal but it’s NFAULT pin didn't respond to this OV error. Besides, register 0x21: FAULTTX, FAULTRX, 0x20: FAUL_TONE, FAULT_HB are already set as 1.  

Best Regards,

Stanley Dai.

  • 0
    TI__Genius 17370 points

    Hi Stanley,

    Please check the datasheet as "the NFAULT output (for base device) and/or the FAULT* interface (for the stack device) signals the fault" since Nfault is referenced to VIO and host mcu side only on a base. In other words, nfault is not a feature implemented for stack devices as typically you would not need it due to no host connection to stack devices.

    Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    TI__Expert 5810 points

    Hi Taylor,

    The issue customer has encountered is that base device's NFAULT pin didn't respond to OV fault signal from stack devices. Customer didn't expect nfault of stack devices.

    Do we have programming procedure regarding to this part for customer one by one checking?

    Many thanks,

    Stanley Dai.

  • 0 in reply to Stanley Dai
    TI__Genius 9301 points

    Hi Stanley, 

    Please ask customer to read TONE_FLT_MSK. These masks will prevent fault signaling if the mask is set. 

    We don't have a specific programming procedure for this. If these masks are not set, then please ask customer to read FAULT_SUMMARY register of all devices and provide the information to be able to further debug. 

    Regards,

    Leslie

  • 0 in reply to Leslie Marquez
    TI__Expert 5810 points

    Hi Leslie,

    Thanks for reply. Below is the setup pf TONE_FLT_MSK value. Is that correct?

    TONE_FLT_MSK:

    #define       TONE_FLT_MSK_FF_REC_MSK                               1

    #define       TONE_FLT_MSK_HB_FAIL_MSK                               1

    #define       TONE_FLT_MSK_HB_FAST_MSK                             1

    Best Regards,

    Stanley

  • 0 in reply to Stanley Dai
    TI__Genius 9301 points

    Hi Stanley,

    These mask bits should be set to 0. If you set them to 1 then the device will mask this faults, meaning the faults won't trigger NFAULT or get reported on FAULT_SUMMARY register.

    I recommend the following:

    • Make sure that faults are not being masked (mask should be 0)
    • Place oscilloscope probe on FAULT+/- lines to confirm faults tones are being transmitted to bottom device when the OV fault occurs
    • Read TONE_FAULT register and FAULT_SUMMARY register before and after fault occurs on all devices (base and stack)

    Regards,

    Leslie