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TPS25751: VBUS Enable function? Source only

Pascal Wessling
Prodigy 20 points
Part Number: TPS25751
Other Parts Discussed in Thread: BQ25756, , TVS2200

Tool/software:

Hey guys,

we are currently in concept phase for a PD sourcing device.

The idea is to use TPS25751D with BQ25756.

We will not have a Battery as a source but a System delivering 12/24V (stil thinking about the Voltage) to source the BQ25756.

Also the system will deliver 5V and 3.3V to supply all the internals of our device.

There will be environmental circumstances in which the System will not be able to supply the full 100W PD for several seconds.

The idea now was, in these seconds, to shut down VBUS over some kind of enable Signal/PIN. We dont want to turn of the whole BQ and TPS chip by cutting their supply voltage as the TPS also will be used for SSMUX control etc.

We only want to signal the PD arrangement, that in these seconds the system does not have the Power to source PD.

Also I am still trying to figure out how to tell the setup that it should be source only. No Sink at any time. Either by Hardware or Software. Maybe I just didnt read it but the documentation is a lot and sometimes you just get lost in it =D

Thank you i advance.

  • 0
    TI__Mastermind 35646 points

    Hi Pascal, 

    Can you provide additional details on what kind of application is this for? 

    Pascal Wessling said:
    The idea now was, in these seconds, to shut down VBUS over some kind of enable Signal/PIN. We dont want to turn of the whole BQ and TPS chip by cutting their supply voltage as the TPS also will be used for SSMUX control etc.

    If VBUS disconnects, typically any other connection (i.e. CCx, USB, etc.) will also disconnect as well. Just to clarify, are you looking for a method to cause a port disconnect by disabling TPS25751 PPHV? 

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 20 points

    Hi Raymond,

    in case of a surge on our power input we would have to handle 150V instaed of 24. normally this is doable but with over 400W output power as we plan... it would be a pretty big curcirty and a lot of heat....

    So our idea was is this case to disable the Power Outputs (VBUS) to the USB-C ports (4 of them). In this scenario we would only need to protect lets say 50W for everithing that is not VBUS.

    Easyest way would be a FET in series With VBUS and in case of surge event simply open VBUS, but I am a bit concerned how Source and Device will react, because normally this should not be like that.

    Hope I could clearify this a bit and you know what I mean.

  • 0 in reply to Pascal Wessling
    TI__Expert 8310 points

    Are you using TVS devices eg. TVS2200 for surge protection on VBUS?

  • 0 in reply to Ghouse Mohiuddin23
    Prodigy 20 points

    Hi Ghouse,

    yes we are using something like this (FET based TVS). But our surges can be 151V over 200ms with V clamp of 35V.

    With our proven equation we get a Power of 6500W that the FETs need to withstand for 200ms in over 60°C. So this is going to be pretty big in size.

    This is wwhy I was asking.

  • 0 in reply to Pascal Wessling
    TI__Mastermind 35646 points

    Hi Pascal, 

    Are you expecting these surges to reach the PD controller and potentially the USB-C ports? Just to note, TPS25751D cannot withstand 151V on its PPHV pin, the absolute maximum allowed on PPHV is 28V. Exposing any higher voltage on TPS25751 PPHV will result in damage. 

    Raymond Lin said:
    If VBUS disconnects, typically any other connection (i.e. CCx, USB, etc.) will also disconnect as well. Just to clarify, are you looking for a method to cause a port disconnect by disabling TPS25751 PPHV? 

    Just also want to re-elaborate on this point, removing VBUS by disconnecting/disabling the TPS25751 power path will also cause a port disconnect which will also result in USB data disconnect. USB data connection will not occur until VBUS is re-applied.

    Thanks and Regards,

    Raymond Lin

  • 0 in reply to Raymond Lin
    Prodigy 20 points

    Hey Raymond,

    of course these surges will not reach the TPS or BQ devices.

    But as you said...if I disable PPHV (Power path) then also Data will be disconnected.

    Do you see any other way to solve my problem? without the loss of data connetion? 

  • 0 in reply to Pascal Wessling
    TI__Prodigy 510 points

    Hi Pascal,

    TI USA is off on 4th July, we will share a response to you early next week.

    Thanks and Regards,

  • +1 in reply to Pascal Wessling
    TI__Mastermind 35646 points

    Hi Pascal, 

    It's not possible to maintain USB data connection without VBUS connection according to USB PD and USB Type-C specification. This is for safety reason in cases of overvoltage, overcurrent, etc. in order to protect both connected systems. 

    Thanks and Regards,

    Raymond Lin