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TPS22990: Ringing when OFF

Hirotsugu Kobayashi
Mastermind 9540 points
Part Number: TPS22990

Hi, team.

When turning on / off 3.3 V with TPS22990 with VIN = VBIAS = ON, ringing occurs at VIN when it is off.
Is the waveform measured by the evaluation board, is there a countermeasure method?


If Vbias is less than 2.5 V, will the IC shut down?

BR

  • 0
    TI__Genius 15780 points

    Hi Hirotsugu,

    Yes, when VBIAS is brought below 2.5V, there is a point where the device shuts down. As for this ringing behavior, we have not seen it before.

    What may be happening is that the input is decaying until the switch is turned off (low VBIAS voltage). At this point, the load is disconnected and the input voltage jumps up. This then turns the part back on, connects the load, and drops the voltage. This cycle continues until the input voltage is low enough to not get affected by this. Judging by the negative voltage on VOUT, I would also say that the inductance of our PCB traces is also affecting the magnitude of the ringing.

    As far as countermeasures go, you could add some capacitance to the system or shorten your PCB traces if possible.

    Thanks,

    Alek Kaknevicius