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Original question:

BQ25792: About operation when the watchdog timer expires

BQ25792: I am using BQ25820 module for 1C rate charging In BMS, but a issue occurs. 1. During charging started – BQ only charged battery with ex: 0.3C, 0.5C or 1C etc., but only charged for 40sec of watchdog timer. After this automatically charging stops a

priyanka patidar
Prodigy 20 points
Part Number: BQ25792
Other Parts Discussed in Thread: BQ25820

Tool/software:

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  • 0
    TI__Mastermind 32491 points

    Hello Priyanka,

    Did you try disabling the watchdog timer?

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 20 points

    1. During charging started – BQ only charged battery with ex: 0.3C, 0.5C or 1C etc., but only charged for 40sec of watchdog timer. After this, automatic charging stops and hold last value into the buffer.

    2. Why is this happening? And what is the correct value to write in the register for the service watchdog timer in proper timing?

    before charging

    ID_CHARGER_CONTROL_11 = 0XE0;              //prev CE config with pg pin, set 0xE0
    ID_TIMER_CONTROL_9= 0X0C;
    wd_reset condition:
    ID_CHARGER_CONTROL_11 = 0XE1;
    charging enable command:
    ID_CHARGER_CONTROL_11 = 0XE1;
  • 0 in reply to priyanka patidar
    TI__Mastermind 32491 points

    Hello Priyanka,

    priyanka patidar said:
    2. Why is this happening? And what is the correct value to write in the register for the service watchdog timer in proper timing?

    You will need to disable the watchdog timer or rewrite to the charge register every 40sec to avoid the watchdog timer from resetting the charge current.

    This is the expected behavior, everytime the watchdog timer expires, the charge current will reset.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 20 points

    when I reset the watchdog timer, I set in charge control register 0xe1, means

    0th bit- En_chg = 1, 

    1st bit - EN_IBAT_LOAD = 0,

    2nd bit- en_hiz = 0,

    3rd bit -en_chg_bit_reset_behavior = 0,

    4th bit -dis_ce_pin =0,

    5th bit - wd_rst = 1 (reset),

    6:7 bit - vrechg = 11 (97.6%)

    This wd_reset condition is mentioned in different substates, which are executed every 30 sec. 

  • 0 in reply to priyanka patidar
    TI__Mastermind 32491 points

    Hello Priyanka,

     

    It looks like I’m already supporting this question throughemail. I will post this response in both, feel free to answer in either through E2E or email.

    • It looks like you marked the E2E as resolved, can you confirm?
    • I see you’re using the wd_reset bit on the BQ25820, does this resolve the issue or does the issue still occur when using this approach?
    •  Do you see any changes from changing execution time from 30sec to 20sec?

     

    Best Regards,

    Christian.