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BQ25798: Dynamic Power Management

Hazar Mutgan
Prodigy 70 points
Part Number: BQ25798

Tool/software:

hi,

i supply the bq25798 with a USB-C PD adapter,. 15V,3A 45W.   i do have the battery connected and system is supplied via VSYS. after the VSYS i have boost converter that outputs 12.2V. i have sense resistors for the input/ output of the boost, and usb-power meter in the input. 

usb-meter reads :10Watt
boost input: 20Watt

i wonder why battery supplement is kicked in, since the charger is 45Watts. 

some charger settings:
input voltage limit: 14000mV
input current limit: 3000mA
charging disabled. 

i don't see that much sag, on the vbus. i would assume bq25798 won't enter the supplement mode.

i look forward for any insights.

best regards,

hazar

  • 0
    TI__Guru**** 166116 points

    Hi Hazar,

    The BQ25798 cannot communicate directly with the USB-C adapter. I assume that the adapter has an integrated PD controller chip and/or EP that tells the adapter to output a voltage >VINDPM=14V? Also, I assume that the EN_ILIM bit = 0 to disable the ILIM pin resistor clamp on IINDPM register?  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 70 points

    hi jeff,
    we have a pd controller that negotiates with usb-c pd brick. 
    after that BQ25798 sets the VINDPM value correct. it is 14V in my case. 

    we manually set he IIMPD 3A ( or whatever the maximum we negotiate from the charger) 

    good point with the EN_ILIM = 0, 
    actually we tied the ILIM_HIZ pin to REGN.  so i assumed that clamp is already about 3.2Amp?

    regards,

    hazar

  • 0 in reply to Hazar Mutgan
    TI__Guru**** 166116 points

    Hi Hazar,

    The charger's status and fault registers in REG0x1B to 0x27 report the charger's status.  Register 0x0F reports if the charger is in HiZ mode due to a very serious fault.  

    Regards,

    Jeff