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High freq transient noise

bj4069
Prodigy 70 points
Other Parts Discussed in Thread: TPS54331

I am using a TPS54331 switcher and am seeing noise in the form of regularly spaced (1 us), 100MHz damped sinusoidal transients of about 500 us in duration on the output.  I used switcher pro to design the circuit which lists the cross over frequency as 1.7KHz and the phase margin at 86 degrees.   To isolate the problem I built another board, populating only the switcher circuit.  Whenever power is applied to the input of the switcher I see the transients. 

Do you have any suggestions about what might be causing the transients?

Thanks

  • 0
    TI__Intellectual 2710 points

    Hello,

    This question is not related to SwitcherPro application in particular. But I got the following response from the applications engineer for TPS54331 team:

    This sounds like switching noise. If in fact it is switching noise, great care must be taken when measuring this.  The ground lead must be as short as possible ( < 1cm) and the measurement should be taken directly across the output capacitor. You should contact your local Analog Applications Support Engineer.

     

    Thanks,

    Hetal Joshi

    Senior Developer and Project Manager

    Analog eLab Design Center

    HPA Design Tools

    Texas Instruments, Inc.

     

    TI makes no warranties and assumes no liability for applications assistance or customer product design. You are fully responsible for all design decisions and engineering with regard to your products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning your designs.