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BQ25750EVM: Setting ouputs and reverse mode with Resistors and No Software

Lucas Cranford
Prodigy 30 points
Part Number: BQ25750EVM
Other Parts Discussed in Thread: BQ25750,

I am using the BQ25750EVM and will be using the BQ25750 chip in a final design.  We want to use resistors to fix the number of cells in the battery as well as enable Reverse Mode.  I see in the data sheet how to do this with software and setting bits, but we need to be able to do this via resistors and external circuits.

  • 0
    TI__Mastermind 31420 points

    Hello Lucas,

    I will get back to you tomorrow on this.

    Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    TI__Mastermind 31420 points

    Hello Lucas,

    Thanks for being patient with the wait. Reverse mode on the BQ25750 has to be enabled with I2C.

    The power path switch over from VAC to VBAT is automatic however.

    Let me know if you have any questions about this.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 30 points

    Ethan,

    I have ordered the interface module. (MSP490 Controller).  I have enabled the Reverse Mode and feel that all the criteria are accounted for in the Battery Managment Studio, however the revers mode continues to show "OFF" in the status.

    I have EN_REV enabled, VAC input is removed, I have set IAC_REV to 4000mA, VSTS_REV to 5000mV, my battery voltage is 3.6V and the voltage at the SRN pin is above 3.3V.  Is there another parameter that I am overlooking?

  • 0 in reply to Lucas Cranford
    TI__Mastermind 31420 points

    Hello Lucas,

    Thanks for bringing this to my attention. Can you try increasing the battery voltage to 4V or 5V?

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 30 points

    I placed the batteries in series and am inputting a battery voltage of 7.4V.  Reverse mode will buck the voltage down to the VSYS_REV of 5000mV but will not boost the voltage if I set it to 12000mV

  • 0 in reply to Lucas Cranford
    TI__Mastermind 31420 points

    Hello Lucas,

    We will look into this and we will get back to you tomorrow. Thanks for being patient with this.

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    TI__Mastermind 31420 points

    Hello Lucas,

    I've looked at this in the lab with your test conditions and I'm not seeing any issues. I've got a few suggestions to help debug this:

    Can you replace the batteries with a power supply and see if the power supply works? Almost any DC power supply should work for this.

    Where is the system voltage being measured at? I recommend TP46 to measure the system voltage.

    Is the system voltage being loaded during these tests?

    Best Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    TI__Expert 3070 points

    Hi Lucas,

    Following up from what Ethan suggested and building on that, the power path transfer happens automatically when VAC is removed. The reverse mode needs to be enabled using software and cannot be done by resistors. I have noticed some concerns whch prevent perfect functioning of the reverse mode however the condition you described what not something I noticed in the lab. One thing that you can try that might help you is the EN_AUTO_REV mode. This is the auto reverse mode and in this case, once enabled, the device wil automatically enter reverse mode when the condition arises. Let me know if that works and also let me know if you are able to exit reverse mode when EN_AUTO_REV is on when VAC is plugged in.