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TPS51225C: TPS51225C Overshoot problem

Part Number: TPS51225C

Hello,

My customer is using TPS51225C to generate 3.3V and 5V. However, they found the 3.3V output overshoot which leads to shut-down 2mS after start-up.

Meanwhile, The 5V and 3.3V regulator outputs still work.

Could you suggest any possible reason for further analysis?

Here is schematic of TPS51225C:

This is 3.3V output. As we can see after the 3.3V went stable, there was an overshoot.

B.R

Paul

  • Paul,

    I see customer also submit the same question about this.

    For schematic, recommend

    Vreg5/3 output caps update to 1uf or 2.2uf

    Reserve 0ohm resistors for DRVH/DRVL.

    How about the output caps? Not shown at schematic.

    For the issue. Please probe SW waveforms/5Vout/3.3out together and zoom in the overshoot point.

    Yuchang

  • the caps is on schematic above。

    the sw waveform is below:(POWER IN =12V)

    the DRVH2 and DRVL2 waveform is below:(POWER IN =12V)(yellow is DRVL2)

    the amplification of above waveform:

    the waveform of output 3.3V and  DRVL2 is below:

    thank you for your help.

  • the caps is on schematic above。

    the sw waveform is below:(POWER IN =12V)

    the DRVH2 and DRVL2 waveform is below:(POWER IN =12V)(yellow is DRVL2)

    the amplification of above waveform:

    the waveform of output 3.3V and  DRVL2 is below:

    thank you for your help.

  • the caps is on schematic above。

    the sw waveform is below:(POWER IN =12V)

    the DRVH2 and DRVL2 waveform is below:(POWER IN =12V)(yellow is DRVL2)

    the amplification of above waveform:

    the waveform of output 3.3V and  DRVL2 is below:

    thank you for your help.

  • Hi Anson, Paul,

    From the waveform, I am not sure why Vout goes higher to OVP? value, but after OVP? happen, Low side should be turns on to discharge Vout but seems not.

    Let's sync up this question by Email Yuchang-zhang@tidotcom. meanwhile could you please try to disconnect the system loading(make 3.3Vout no loading) to check whether this issue still happen, and also send me the schematic and layout for review.

    Yuchang

  • It has been fixed. 

    Thanks, Yuchang!