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tps2331 issue

Oliver Ou
Intellectual 2845 points
Other Parts Discussed in Thread: TPS2331

Hi,

We meet an issue on TPS2331 as blow.

When using 2.2nF cap. on GATE pin, TPS2331's Gate driver signal is right and output voltage increases smoothly.

When using 4.7nF or lage cap. on GATE pin, TPS2331's gate driver signal is not right and it works at auto-retry mode.

No OCP and No UVLO occur  at this moment.

From datasheet, we can't find the description about auto-retry mode.  Is there any special protection in this chip?

What can cause this issue? Thanks.

 

schematic, with 6mF output caps

 

Good waveform:

 Fail:

 

 

 

  • 0
    TI__Genius 9415 points

    This is no retry for the TPS2331. This is abnormal behavior because of the large gate capacitance

    The text says 4.7nF but the schematic shows .047uF. The datasheet has some graphs showing gate capacitance to 10nF. If you have 47nF, it could be a problem. Check this capacitor value or try again with known components.

    If you have a 47nF capacitor, it could be that since the gate drive on this part is only 14uA typical. it doesn't have enough current to charge the large capacitor to the full gate voltage. The actual load, or voltage across the sense resistor,  is causing the gate signal to be brought low.  It looks possible in the datasheet block diagram. I'm not sure why the part restarts. It may be that the fault signal is not  generated because the timer didn't  start. The TPS2331 starts again because there is no fault.

  • 0 in reply to Bob Kando
    TI__Intellectual 2845 points

    Hi Bob,

    On customer's board, the issue can be found when using 4.7nF cap.  Maybe the output cap is too large: 6mF.

    We found there is a DV/Dt Rate Protection funciton  in blow block. What dose it mean?  How dose the IC achieve this function?

     

    Thanks.

    Oliver

  • 0 in reply to Oliver Ou
    TI__Genius 9415 points

    The dv/dt protection block refers to a small control over rise and fall time of the gate. This is more edge control than inrush control. It is more appropriate to turn off because of the large current pull down current pulse to turn off the FET.