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BQ25120A: Watchdog interference during system debug

Jeff Calwood
Prodigy 20 points
Part Number: BQ25120A
Other Parts Discussed in Thread: BQ25121A

Hello,

is there a way to disable the device's watchdog during debug ?

I am powering my hardware via VIN (ie a USB charger) and debugging the host. When I hit a breakpoint, after ~50s the BQ's watchdog kicks in and resets all parameters, including the load switch settings. It doesn't seem to matter whether the charger is enabled or disabled via /CD . Any thoughts.

And a (silly?) side question related to this part. There's a PCB checklist at the link below. Why do you recommend all capacitor voltage ratings twice the required voltage ? I can see that for the input side due to overvoltage, but on the PMID or battery side ? Just curious. https://e2e.ti.com/support/power-management/f/196/p/826735/3058136?tisearch=e2e-sitesearch&keymatch=BQ25120A#3058136

  • 0
    TI__Mastermind 21590 points

    Hello Jeff,

    There is no way to disable the watchdog. When the device is placed in Hi-z mode when VIN is absent, the watchdog timer is disabled. This is expected behavior. However, the BQ25121A has the watchdog disabled by default. 

    Twice the required voltage is recommended for safety reasons to ensure transient cases don't cause damage to the capacitor.

  • 0 in reply to Raheem
    Prodigy 20 points

    Thanks for the prompt response.

    I think you are confirming that ONLY in HiZ mode (which implies VIN absent) is the watchdog disabled, correct ?

    Just wanted to confirm that I didn't make a mistake: Disabling the charger (via I2C or via /CD) while VIN is present DOES NOT disable the watchdog, correct ?

    The bq25121A for development is a great find. At first glance, the only other difference is the default output voltage is 2.5V (which my HW could tolerate until I reconfigure it to 1.8V).

    Jeff

  • 0 in reply to Jeff Calwood
    TI__Mastermind 21590 points

    Hello,

    Yes watchdog is only disabled in Hi-z mode which only occurs when VIN is absent.

    No. When VIN is present, /CD only enables or disables charge.

    Yes those are the only 2 differences. You can see the table describing the differences in the BQ2512x family below.

    https://e2e.ti.com/support/power-management/f/196/t/856531