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TPS568215: V3P3 start up by step

SU DANY
Prodigy 70 points
Part Number: TPS568215

Hi Sir

We have design TPS568215 for V3P3 power rail, and we found there is step when start up. Please see the attached screen shot.

Could you provide your adivce and check the schematic if there is design issue. 

V3P3 power start up

TPS568215_V3P3

Thanks a lot

Danny

  • 0
    TI__Expert 7320 points

    Hi Danny,

    The waveform looks strange.

    Could you please help to test the Vin, EN, PG, FB pin voltage and load current in the meantime?

  • 0
    Prodigy 70 points

    Hi Athos

    I have measure the VIN. EN, PG,FB pin as scree shot firt. could you also help to view schematic design.

    VIN_VOUT_EN_PG

    VOUT_FB_EN_PG

    Is it possible other power rail rise up befor V3P3_AUX and interference V3P3_AUX?

    Thanks

  • 0 in reply to SU DANY
    TI__Expert 7320 points

    Hi Danny,

    Yes, you can see the output voltage rise up before Vin and EN, so the first step of Vout is not from the SW pin but coupling from the loading side.

    You can also check the SW waveform. I think the voltage of SW pin don't have any pulse and just follow the Vout.

    You can confirm the root cause by disconnecting all the loading side and see which side have ~1V voltage.