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About Flickering/Fluctuating Output in boost/OTG mode - BQ24296

Pritam Kalaimani81
Intellectual 725 points
Other Parts Discussed in Thread: BQ24296

Hi

I am running my system in Boost mode, I have been successfully able to configure my BQ24296 EVM & my hardware board  to obtain a O/P voltage of 5V. But however when I connect the load to my hardware board at VBUS or PMID, I find that the O/P is flickering/fluctuating. I cannot observe this kind of behaviour with my EVM but this is only happening  with my hardware board. In terms of schematics and passive component values, I have taken complete reference from the schematics of the EVM, Somebody please pin point the issue here.

Thanks in advance for the help

  • 0
    TI__Mastermind 46551 points

    More info is needed to do further investigation. Assuming your design is the same as the 296 EVM,

    1)       Please provide all register values when it happens and check if there's any fault.

    2)       What are you VBAT, VBUS, IVBUS (i.e. OTG load current), VSYS, ISYS?

    2)       Please provide waveforms for VBUS, IVBUS, SW, VBAT, IBAT.

    Thanks!

  • 0 in reply to Ning T
    Intellectual 725 points

    Hi

    Thank you for the response.

    My register values That I have assigned is given below

    1) register 0x01  - 0x20

    2) register 0x05 - 0x00

    3) register 0x06- 8f

    My VBAT value is 3.8V, VBUS value is 5V, IBUS value is 2A. VSYS value is 3.8V, ISYS value is 200mA.

    Please let me know if there are any mistakes with respect to the above configuration.

    thanks in advance

  • 0 in reply to Pritam Kalaimani81
    Intellectual 725 points

    Well, sorry about my my mistake. We will not consume more than 1.3A when system is run in boost mode at IBUS.

    Eagerly waiting for your reply.

    Thanks in advance.

  • 0 in reply to Pritam Kalaimani81
    TI__Mastermind 46551 points
    bq24296 can support USB OTG with Adjustable Output 4.55 V to 5.5 V at 1 A or 1.5 A. Your OTG is too high (IBUS=2A) and your OTG current is set to 1A (REG01[0]=1A). Please read REG08 and REG09 to check fault status. Thanks!
  • 0 in reply to Ning T
    Intellectual 725 points

    Hi

    Thank you for the tip.

    Although I am able to get 5V at VBUS. Sometimes I'm also finding that I do not get 5V at VBUS. and when I read the registers 0X08 & 0X09, I find that the values are 0, currently my register values are as follows:

    1)  Register 0X01 - 0X27

    2) Register 0X05 - 0X00

    3) Register 0X06 - 7F

    After I run the code and read the register values of 0X08 & 0X09 I'm getting 0, I do not get any values. Why is that.

    Thanks!

  • 0 in reply to Pritam Kalaimani81
    TI__Mastermind 46551 points
    If REG08=00, that means the device is not in OTG mode.
    Referring to page 22 of the d/s, to verify real time fault, the fault register REG09 should be read twice to get the real condition.
    Are you using real battery to test the OTG mode or a lab supply to simulate battery voltage?
    Please provide all register values if possible.
    Thanks!