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Recovery from UVP status on TPS54295, TPS542941, TPS54394 and TPS54395

Other Parts Discussed in Thread: TPS542941, TPS54394, TPS54395, TPS54295

Hi

My customer has used TPS54295 for current production models and they are now considering TPS542941, TPS54394 and/or TPS54395 for next models.

When they designed with TPS54295 last year, they had seen the problem that TPS54295 can not recover from UVP situation due to the instant voltage drop of Vin.

(When instant voltage drop of Vin occurred, Vout goes below the threshold of UVP and TPS54295 shut off swithches. However, in customer design, EN is connected to Vin via resistor, then the voltage of EN was NOT discharged enough during instant voltage drop (remain high). As a result, even though Vin was recovered, TPS54295 still stayed in UVP mode.)

For new models, I have explained that TPS542941, TPS54394 and/or TPS54395 have different protection mode, called Hiccup mode, so same problem can not be expected. However, in order to proof this, customer would like to check the waveforms from actual device evaluation.

Do you have any good waveforms which can clearly show different protection behavior of these devices?

TPS54295: latch off

TPS542941, TPS54394 and TPS54395: Hiccup mode

Thank you for your support in advance.

Regards,

Ken

  • You are correct, these later devices have hiccup mode for UVP.  I have searched my database, but do not have those specific waveforms (they are not part of what we usually supply for datasheet).  I could possibly compare them during an over current condition and recovery.  But I would have to order EVMs, so it may take a week or so.

  • Hi John,

    Thank you for your reply. Understood that you have no waveforms there.

    I and my colleague try to perform some evaluation by using your evalutaion board.  Can you check following procedure that I summarized for replicating behavior?

    My intention is to see the differences of protection behavior as simple as possible, so I don't intend to replicate the instant voltage drop of Vin to cause UVP protection.

    Vin:12V

    Vout: as default of evaluation board / no load

    EN: Apply separately to keep "high"

    When Vin is decreased manually, it's assumed that device can not maintain output voltage and could trigger UVP protection. (before trigerring UVLO)

    In this situation, EN is remained high, so we can see the differences. Do you have any comments?

     

    Other than above, I need to use instant voltage drop of Vin with the combination of P-ch and N-ch FET.

    Thanks,

    Ken

  • Hi John,

    Today, my colleague has performed following experiment to make sure the different protection behavior on TPS54295 and TPS54395.

    ------------------------------------

    EVM: TPS54925EVM and TPS54395EVM

    Vin: 12V

    EN: 5V from external supply

    Vout: Electrical load

    Observation:

    * When he incread the load current manually, it seems that device goes into UVP protection mode then stop switching.

    * After decreased load current, TPS54395 re-started operation correctly, while TPS54295 remained no switching mode.

    ------------------------------------

    From his statement above, I assume following scenario. When the load current was increased, both devices go into OCP protection and keep low side FET on state.

    However, since he still draw the current, the output voltage falls and got lower than UVP threshold, then devices go into UVP protection.

    Because of TPS54395 has Hiccup topology, device can start operation again, once OCP situation is removed.

    But for TPS54295, external toggle on EN pin is required, so remained in protection mode.

    Do you think this is reasonable?

     

    Thank you for you support in advance.

    Regards,

    Ken

  • Yes.  That is what I would expect.

  • Hi John,

    Sorry for my long silence.

    We did quick measurement by using your EVM and saw waveforms as attached.

    Thank you for your support on this matter.

    Regards,
    Ken

    (attached is short version, if you want to review full version, pelase contact me separately.)

    6787.130514-TPS54295-5439x-ProtectionBehavior.pdf

  • Thanks, do you need further support?

  • Hi John, no at this moment! Good night.

    Regards,

    Ken