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TPS48111Q1EVM: TPS48111Q1EVM questions

Alex Teryohin
Prodigy 115 points

Part Number: TPS48111Q1EVM

Hello.

I have some questions regarding the EVB design:

https://www.ti.com/lit/ug/sluuck8a/sluuck8a.pdf?ts=1677672815365&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FTPS48111Q1EVM

1) What is the purpose of diodes OR'ing at the Vs input (D10 & D11)? I suppose it is done to power the component after the input voltage has been turned-off, and the output is still charged, but why it is needed? Should it prevent from some damage?

2) One of the purposes of this driver is inrush current protection by using pre-charge or/and inrush current limiting. Why, however, three capacitors of about ~50uF net capacitance have been added to the input of the inrush protection, overriding the inrush protection effect?

Sincerely,

Alex

  • 0
    TI__Guru** 107611 points

    Hi Alex,

    Thanks for reaching out!

    1A) To power the IC when Vin goes away so that it can support bidirectional current flow.

    2A) The input capacitors are added as general use case. you can remove them if your case wants to limit inrush current.

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Prodigy 115 points

    Hi Rakesh.

    1) If so, I think there is some problem with this bidirectional flow. In order MOSFETs will be turned-on, there following should happen: Vs should be present, EN pin should be above 1.1V, the INP should be above 2V. In case Vin is switched-off EN drops down (since it is the input division of Vin), and INP will drop as well, since VAUX turned-off as well. Only Vs will be powered from output, but this is not enough to hold MOSFETs opened. Anyway, if we use some contactor at the input, the current will not be able to flow in opposite direction. This can work in case the driver is powered directly from power supply (not through some switch).

    2) OK. So they are not needed, if I understand you right.

    Sincerely,

    Alex.

  • +1 in reply to Alex Teryohin
    TI__Guru** 107611 points

    Hi Alex,

    1A) yes, input has to be powered to enable the IC and allow reverse current flow. For example, charging a battery in reverse direction and powering load from battery in forward direction.

    If input supply is not there, then EN has to be tapped from VS node to enable the IC

    2A) Correct

    Best Regards,

    Rakesh