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BQ25792: DOUBT REGARDING VBUS PIN

Anasur Rahman
Prodigy 30 points
Part Number: BQ25792

Hi ,

   1.I have one doubt regarding the VBUS pin.Shall I connect USB TYPE-C directly to VBUS of the BQ25792 without any USB PD Controller.

   2.In my apllication we are getting power from either type-c or battery. When I power on the board through battery,it is working fine.But whenever i try to power on the board through type c,i am getting some acoustic noise from the inductor which is connected between BTST1 nad SW2.

  • 0
    TI__Guru**** 166996 points

    Hi Anasur,

    Regarding 1, no.  Since the BQ25792 does not have CCx input pins, a type C communication chip or port controller is required.

    Regarding 2, I do not expect the USB-C to be able to output power without one of the chips above.  The inductor is required for the buck-boost converter.  Disabling PFM mode with REG0x12[4] = 1 might remove the noise.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 30 points

    Point2, here i am using PD controller but still i am getting the same acoustic sound from the inductor.Don't know why the sound is coming...?

    How can i disable the PFM mode .Is the any GUI is there if its there please send the GUI link.

    The i2c lines are connected between the PD controller and battery charger IC

  • 0 in reply to Jeff F
    Prodigy 30 points

    Point1, Shall i give supply to the VBUS pin using an external Power supply...?

  • 0 in reply to Anasur Rahman
    TI__Guru**** 166996 points

    Hi Anasur,

    There is an online GUI at https://www.ti.com/tool/TI-CHARGER-GUI and it requires the communication box at https://www.ti.com/tool/USB2ANY.  You don't need the GUI and could read and write using any I2C engine. 

    To disable PFM mode, the I2C engine writes a 1 to REG0x12[4] at address 0x6B.  But your issue could be due to the charger's input current regulation setting and/or input voltage regulation setting not agreeing with the output voltage and/or current that the USB-C is providing. 

    I suggest using a bench power supply with known output current limit and voltage that agrees with the charger's settings.  The charger auto detects input voltage at power up for setting VINDPM to 0.7V below the detected input voltage.  The input current limit is set to the lower of the value per ILIM_HIZ resistors or D+/D- detection.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 30 points

    I have one more doubt about the VSYS.

    What will be the VSYS voltage for 1s,2s,3s & 4s...? and what is the max input current of BQ25792...?

  • 0 in reply to Jeff F
    Prodigy 30 points

    In our design the pin CE is grounded.In this condition if  i float the bat pin and connect the usb typc alone whether i face the problem of VSYS voltage fluctuation...?

  • 0 in reply to Anasur Rahman
    TI__Guru**** 166996 points

    Hi Anasur,

    VSYS = max of MINSYS voltage or V(BAT)+200mV when battery is attached.  In supplement mode due to heavy load current on SYS, V(SYS) drops to battery voltage.  If there is no battery attached and charge is enabled due to /CE pin and CE bit and the TS pin is disabled, then V(BAT) pulses up to BATREG and V(SYS) pulses between MINSYS and BATREG+200mV.

    Max input current of 792 is 3.3A.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Prodigy 30 points

    I'll have one doubt regarding the REGN LDO. In datasheet it is mentioned as Vregn=5V. But in our board we are getting around the 5.45 volt

  • 0 in reply to Anasur Rahman
    Prodigy 30 points

    And also about ILIM_HIZ.The term ILIM_HIZ is for limiting the current which charges the battery or the limitting the input current of the charger Ic.

  • 0 in reply to Anasur Rahman
    TI__Guru**** 166996 points

    Anasur,

    REGN output voltage spec is shown below:

    Your IC is out of spec.  Do all IC's show that?

    Regarding ILIM_HIZ, it limits the input current which indirectly limits charge current if the system load + battery charger current requires more power than the input voltage and limited input current can provide.

    Regards,

    Jeff