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BQ25570EVM-206: Buck output

Jonathan Navor
Genius 9475 points
Part Number: BQ25570EVM-206

 Hi Expert,

Good day!

I know the buck output is set to 1.8V by resistors and our cusotmer want to raise the output to 3.3V, how could we change the resistors and by what amount? Eg Rout1 and Rout2.

Do we need PFET at all?
eg, the PFET i am thinking of is;
1.between VSTOR and VBAT to prevent overchange
2.between VSTOR and MCU so that there is no loading on VSTOR until VSTOR > VBAT_OK_HYST

Thank you in advance.

Best regards,

Jonathan

  • +1
    TI__Guru**** 166176 points

    HI Jonathan,

    The spreadsheet at the link belows helps size the resistors.

    https://www.ti.com/lit/zip/sluc484

    The internal resistor between VSTOR and VBAT is to prevent battery overdischarge not overcharge.  If the battery has its own internal protector, that FET is not needed and VSTOR can be shorted to VBAT.

    The external PFET to isolate the load at VSTOR until VSTOR is above VBAT_OK is highly recommended.  You will also need an NFET, driven by VBAT_OK output, to pull down the PFET gate to turn on the PFET.

    Regards,
    Jeff