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BQ25756: Which power supply is powering the system

Xavier
Prodigy 100 points
Part Number: BQ25756
Other Parts Discussed in Thread: PMP41062, , BQ25731

Hi all,

I now have a design that needs to use Type C or battery to power the system work.

However, I found in the reference design PMP41062 that there seems to be two power supplies that can power the system, VSYS and P_OUT, where VSYS is supplied directly from VBUS.

Q1.  I am now wondering which one of them can power the system behind?

In the BQ25756 datasheet, P_OUT seems to be able to power the system, but I'm not really sure .

Q2.  Another question is whether the system power supply of the BQ25756 can be changed by modifying the registers to change the value of the power supply voltage, as in the case of the BQ25731.

I look forward to your reply.

Best Regards，

Xavier.

  • +1
    TI__Intellectual 2630 points

    1. It seems like VSYS is the input and P_OUT is the output and I would suggest using P_OUT.

    2. Yes that is possible.

  • 0 in reply to Utsav Gupta
    Prodigy 100 points

    Hi Utsav,

    Thank you for your answer.

    Additional questions,

    Q1. In the previous image, the P_OUT sources are different, coming from the front end (Fig. 1) and the back end (Fig. 2) of the Rsr，which of these two is more recommended？

    Q2. Please also tell me which register I can modify to change the system supply voltage of the BQ25756.

    Best Regards，

    Xavier.

  • 0 in reply to Xavier
    TI__Intellectual 2630 points

    1. We recommend to use the one from the back end.

    2. You don't need to modify a register setting to change the input voltage. As long as the voltage is between the UV and OV range it should be fine. For output voltage, please modify the VOUT_REG register.