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TPS25750EVM: Regarding VBUS pin configuration of TPS25750D

BHUPENDAR SINGH
Intellectual 265 points
Part Number: TPS25750EVM
Other Parts Discussed in Thread: TPS25750

In our design we are using using TPS25750D USB Type C controller and Power ing through a 12V DC adapter with USB C type D Conn.

In datasheet of TPS25750D , it is mentioned that  VBUS pin 32 and Pin 33  are output type Pin and are 5-V output from PP5V input to LDO. Bypass with capacitance CVBUS to GND.

But in reference design mentioned in EVM board of TPS25750, They are shorting the VBUS pins 32 and 33 with VBUS_IN Pin which is connected to a 12V input supply from USB C conn.

As per our understanding if we have 5V DC input at USB C connector we can connect it to PP5V pin and that case can short VBUS pin pin to VBUS_IN . But in case we have 12V upply input at USB C con  we shouldn't connect 12V supply connected to VBUS_IN pin  to 5V output VBUS Pin.

So want to confirm if it is ok to short VBUS pin with VBUS_IN pin , in case we have 12V input supply to USB C conn and there is no supply input at PP5V pin ( PP5V pin is connected to GND through 10uF cap) .

And what is purpose behind shorting the VBUS pin to VBUS_IN pin in EVM board ref design.

Please help here.

  • 0
    Intellectual 265 points

    Also take a case where we are just Power sink ( consumer) application only.

  • 0 in reply to BHUPENDAR SINGH
    TI__Mastermind 32831 points

    BHUPENDRA,

    If you are using the TPS25750 as a SINK, then the PP5V path will not be used.

    The VBUS to VBUS_IN shorting is used to lower the impedance on the powerpath between the two power paths inside of the package.

    We have a FAQ link that shows exactly how to configure the TPS25750 into a sink configuration exactly like you have shown in your figure that provides a lot more information

    [FAQ] TPS25750: How do I create a PD UFP or Sink with an EEPROM?

  • 0 in reply to Chuck Branch
    Intellectual 265 points

    Thanks Chuck! So is there anything else VBUS is doing by shorting it to VBUS_IN apart from lowering the impedance. As  in datasheet of TPS25750 it is mentioned that VIN_3V3 or VBUS are the power to generate Core and IO supply for TPS25750 through an Internal LDO. As we don't have any external supply connected toVIN_3V3 pin , does VBUS need to be connected to VBUS_IN because of that.

  • 0 in reply to BHUPENDAR SINGH
    TI__Mastermind 32831 points

    One of the pins is for high power and the other has several uses, including voltage sense, so it is critical that both of them be shorted together by a low impedance connection for optimum performance.

    In the case where the TPS25750 is used as a sink, there is an internal regulator that will generate all local supplies.  The two that are visible on external pins are LDO_3V3 and LDO_1V5.  When LDO_3V3 is present, then the part has in internal power network that will select this voltage instead of the one venerated internally from VBUS.

    If you are always a sink, then there is no need to supply PP5V or VIN_3V3, but it is important to connect that capacitor to VIN_3V3 and not connect it to any other devices if this is the case.

    LDO_3V3 will supply sufficient current to power the external EEPROM.  The FAQ I mentioned above shows all of the connections necessary for a sink only application.

    Regards,

    Chuck