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TPS549B22: Feedback resistors

Part Number: TPS549B22
Other Parts Discussed in Thread: TPS548B22


For the part “TPS54922RVFR” provide the pin configuration for unused PMBUS pins.

 Also, for feedback resistor section, In datasheet it is mentioned that If the output voltage set point is one of the 16

available reference and boot voltage options, no feedback resistors are required for output voltage programming.

But in webench simulation, 10ohm feedback resistor is connected. Kindly confirm.


Dharini V

  • Hi ,

    You can float the unused PMBus pins. In case you're not aware, we also have a non-PMBus equivalent device TPS548B22.

    The 10ohm resistors Rrsp and Rrsn are optional but serve a few functions:

    1) Break the remote sense nets so that in layout the RSP trace does not inadvertently flood with any VOUT pours and the RSN trace does not flood with any PGND pours/planes in the path to the remote load.

    2) These resistors with Cfilt capacitor form a differential low pass filter that will help filter out noise that has coupled onto the differential pair traces.

    3) Rrsp can also be used as an injection resistor for Bode plot measurements.

    If you are not concerned with the above functions, you can directly connect from your load sense point and load GND point back to the RSP and RSN pins. But we recommend to keep placeholders for these resistors (and Cfilt filter cap).