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TPS546D24S: Debug the output voltage problem

Part Number: TPS546D24S

Hi,

I have a customer using TPS546D24S, this chip does not have FB pin, can only be adjusted by IIC? He wants to output 0.88V voltage, can it be achieved?

Many thanks~

  • Hi Rhea,

    This device uses the VOSNS and GOSNS pins to sense the output voltage and regulate it to the correct voltage. The feedback signal is divided internally and controlled by the VOU_SCALE_LOOP setting. This gives a wide range of programmable Vouts with a small step.

    Vout can be programmed using pin-strapping on the VSEL pin, or by using PMBUS. The pin strapping resistor on VSEL to give 0.88V are 56.2k from VSEL to AGND, and 187k from VSEL to BP1V5. 

    You can also set the output voltage over PMBus, store the value into the NVM, and change the PIN_DETECT_OVERRIDE setting so that it defaults to the NVM value instead of the pin-strapped value.

    Can you share the schematic?

    Thanks,

    Joseph

  • Hi Joseph,

    The customer feedback calculated below is not 0.88V

  • Hi Rhea,

    You highlighted the wrong column + row in the tables above.

    The Vout calculation is as follows:

    Rbot=56.2k, R_bp1v5=187k

    R2G code=13

    Divider Code=1

    Vout_command step= 0.01V

    Vout_command step (offset)=0.75V

    Then plug into the equation:

    13 = (Vout - 0.75) / 0.01

    Vout = 0.88V

    Let me know if you have any questions regarding this calculation.

    Thanks,

    Joseph

  • Hi Joseph,

    When R2G code is 13, OFFSET is 4.2 and step is 0.04, which is not the value you mentioned?

  • Hi Rhea,

    There are two unique codes that are programmed into each pin strapping pin. 

    The R2G code, which is set by the resistor to AGND. And the resistor divider code which is set by the resistor to BP1V5.

    The resistor divider code in this case is 1, which selects the Vout_command step and Vout_command step (offset). Then the variable CODE in the equation above is set equal to the R2G code value=13 in this case.

    Thanks,

    Joseph