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TPS2H160-Q1: Ringing at the end in driving capacitive loads

Takashi Onawa
Genius 13200 points
Part Number: TPS2H160-Q1

Hi Team,

I just read the SLVAE30E and didn't understand well the reason why Iout ringing when driving capacitive load
Could you supplement what going on the ringing state?

Due to the FET heating up during this charging period some ringing occurs at the end because of the high temperature transition between the internal MOSFET modes of operation, however this poses no risk to the system due to the short transient length.

Regards,

Takashi Onawa

Regards,

Takashi Onawa

  • +1
    TI__Genius 16390 points

    Hi Onawa-san,

    Thanks for reaching out. When it's charging the cap, it's doing the current limiting. The FET is not in linear region anymore, but in saturation region. In this state, the effective Rds-on is very high for the device, and FET can go into thermal shutdown state with longer operations in such states. When the device hit thermal shutdown, it will shutoff it self. If the IC is in auto-retry state, it will keep bringing itself back up and may go back again if thermal is high. This is the FET on and off towards the end of the charging.

    This won't happen everytime - depending on the current limit setting and the cap size.

    Please let me know anything else we can clarify.

    Regards,

    Yichi

  • 0 in reply to Yichi Zhang.
    TI__Genius 13200 points

    Hi Yichi-san,

    Thanks, that makes sense for me.

    Then, I have one more questions on the behavior.
    In the app note mentions the behavior should be no risks. However, the device's thermal shutdown threshold is 160~175C against Tj_max=150C.
    Can we say that is really no risks?
    Or should we recommend using smaller cap such the capacitive load drive with high side switch device?

    Due to the FET heating up during this charging period some ringing occurs at the end because of the high temperature transition between the internal MOSFET modes of operation, however this poses no risk to the system due to the short transient length.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Genius 16390 points

    Hi Onawa-san,

    The thermal shutdown should be protecting the device from damaging or degrading, but I would try to avoid it if I can.

    Regards,

    Yichi