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Original question:

TPS22990: Ringing when OFF

TPS22990: TPS22990

Gary Chien46
Prodigy 20 points
Part Number: TPS22990

Hi Guys,

I got some problems when my system is power down. 

When VIN (+5V_SBY) is around 1.6V, discharged slowly as figure, there is a spike on Vout around at 1.26V.

At this time, Von is around 0.74V. Please advise what is happening and how can I avoid this symptom. 

ThanksTPS22990_5VS_SPIKE.pdf

  • 0
    TI__Guru** 105211 points

    Hi Gary,

    We will get back to you early next week.

    BR, Rakesh

  • 0
    TI__Mastermind 31265 points

    Gary,

    Could you try to increase the output capacitance of the design to something like 100uF for testing here? What might be happening here is that the input is turning off suddenly and there is a reverse current condition. We generally recommend a 10:1 input-to-output capacitance ratio to prevent against conditions like this.