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TPS53659: Getting Spikes in Oscilloscope

Siddhi Sawant
Intellectual 310 points
Part Number: TPS53659

Tool/software:

Hi Team,

I am using SN1701022 controller IC.

In Fusion Power Designer Software, Monitor GUI we are getting correct steady waveform for output voltage of 1.8V

But when we checked in oscilloscope, it is showing Spikes in output voltage of P1V8_AUX (1.8V). I am attaching the image of error below which is captured in oscilloscope.

Can this be corrected using Load Line resistor value in Fusion GUI?

I found in TRM, some commands like MFR_SPECIFIC_07, VOUT_DROOP, and MFR_SPECIFIC_14 can be used to adjust output voltage in such cases.

Will this work in our case? Will that solve the voltage spike issue that we are facing?

For VOUT_DROOP in Hex, it is corresponding to particular DC load line resistor, so how to select this value for particular application?

Thanks,

Siddhi

  • 0
    TI__Intellectual 2115 points

    Hi Siddhi,

    We will look into this and get back to you in a day or so.

    Regards,

    Troy

  • 0 in reply to Troy Johnson
    Intellectual 310 points

    Hi Troy,

    Any update?

    Thanks

    Siddhi

  • 0 in reply to Siddhi Sawant
    TI__Intellectual 2115 points

    Hi Siddhi,


    VOUT_DROOP sets the DC load line, which affects how the actual output voltage varies from VOUT_COMMAND while under a load current. It should be set such that the actual VOUT measured or reported in Fusion is acceptable for your purposes.

    The MFR_SPECIFIC_07, VOUT_DROOP, and MFR_SPECIFIC_14 commands tune the output voltage feedback and response to transients. Changing them will affect how the controller responds to a change in load current and VOUT, but won't prevent the drop in VOUT your seeing from occurring.

    I would recommend checking the switch node voltages when the drop happens to try and get some insight into why VOUT is dropping. You said your scope is connected to P1V8_AUX. Is this directly connected to VOUT? If not then I would recommend checking as close to the output inductor and capacitators as you can, to remove the risk of some other component changing your voltage reading.

    Regards,
    Troy