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TPS548D22: Transient Response

jiajun ren
Prodigy 50 points
Part Number: TPS548D22

The input is 12 V，and the output is 2.5 V. The transient loading is from 2 A to 10 A. Why the overshoot followed by an undershoot, and the undershoot followed by an overshoot, no matter what the inductor I changed to?

  • 0
    TI__Mastermind 48200 points

     

    It would help if you could share your schematic.  Typically this would be the result of low phase margin in the loop, due to high propagation delay between the output terminal of the inductor and the sensed output voltage, added filtering in the feedback path, or insufficient output capacitance given the Inductor and ramp generator selected.  They schematic could help identify which of those is the likely cause.

  • 0 in reply to Peter James Miller
    Prodigy 50 points

    The filter capacitor in feedback path is not on board.

  • 0 in reply to jiajun ren
    TI__Mastermind 48200 points

     

    The circuit appears to be set-up for remote sense.  A long power distriibution path with remote capacitance can negatively affect the loop performance by adding a parasitic filter and related delays to the power-path, so I would recommend checking that.

    However, if the schematic showin is complete, I would recommend changing the ramp generation resistor from 1x to 3x by changing MPR23875 (FSEL to AGND) from 22.1kΩ to 37.4kΩ.

    You may also want to consider adding a 220pF capacitor in parallel with MPR23891 (between VOSNS and RSP) to counter the attenuation of the feedback divider at high frequencies.

    Additionally, if you have an issue with a parasitic L-C in the power path to the remote sense point, you could populate a capacitor in the MPR23878 location to form a high-pass filter with MPR23880, though I don't see a value on MPR23880.