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BQ25792: BQ25792 disables OTG mode when running into IOTG limit

Elen Eisendle
Prodigy 20 points
Part Number: BQ25792

I noticed that when the IC is in OTG mode and a test load pulls more than the limit set in IOTG, instead of limiting the current, it disables the OTG bit. First OTG_UVP_STAT is asserted and then EN_OTG is reset.

Is this the expected behaviour? Because from the documentation I assumed, that it would limit the output current at the set-point. Is there a configuration flag to make it a constant current source?

  • 0
    TI__Guru**** 167196 points

    Hi Elen,

    In OTG mode, an OTG UVP can occur if the load on VBUS is higher than the OTG Limit setting, causing VBUS to drop below the OTG_UVP setting =2.2V.  At this point, hiccup mode starts.  You can disable hiccup mode with REG13b2.  Is your load too much for your battery voltage or current?  The charger regulates the IBAT discharge current using REG14b4-3.  The IBAT discharge regulation defaults to 5A.  Is VOTG*IOTG > IBAT*VBAT/efficiency, where IBAT is clamped to 5A and VBAT drops too low?

    Regards,

    Jeff  

  • 0 in reply to Jeff F
    Prodigy 20 points

    Thank you, disabling hiccup mode did the trick. The load wasn't too much, I just set the OTG current limit to the minimum on purpose to test the constant current capability which made the OTG voltage drop to 1.6V.

  • 0 in reply to Elen Eisendle
    TI__Guru**** 167196 points

    Great!  Glad to know the IC is working as expected.

    Jeff