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TPS65982: Does programming of the TPS65982 affect the path of the SBU1->AUX_P connection

WST
Expert 1015 points
Part Number: TPS65982

I found out on my board that when I make a displayport connection, that SBU1 (K8) is connected to AUX_N (J2) and that SBU2 (L8) is connected to AUX_P (J1). This looks flipped from the Datasheet in Table 4. There is says that AUX_P is connected to SBU1 (3rd column). However this is NOT what I measure. It doesn't seem to matter which CC line is used to make the connection, the Multiplexer doesn't change.

There are some hints that SBU1 -> AUX_N, because on page 84, Figure 79 seems to indicate this.

This isn't a problem on my board because I have a SBU mux that allows me to switch the orientation of the USB-C connector SBU1/2 pins to either go straight through to the SBU1/2 pins of the TI part, or swap.

But I was wondering what is the correct orientation? I measured the connections with a ohmmeter (3 times) when in Displayport mode and I'm sure they are swapped from Table 4. Is there something in the configuration image that changes this?

Thanks,
WST

  • 0
    TI__Mastermind 36756 points
    Hi WST,

    The SBU/ AUX lines are internally muxed based on the display port configuration and display port connection (i.e. 2 lanes + data vs. 4 lanes). Please refer to the VESA DisplayPort Alternate Mode on USB Type-C Standard documentation.

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    Expert 1015 points

    Eric,

       I looked all through that document and didn't see any reason for flipping due to 4lane (C) or 2+2 (D) configurations/pinouts. I have observed that when I connect the USB-C port to a DP device as an DFP_D host, that the AUX_P on the display port connector connects through the TPS65982 to the SBU1 line of the USB-C connector. When I connect the USB-C port to a DP host and then configure as a UFP_D display port device, then the TPS65982 connects the SBU1 line to the AUX_N line of the display port connector. However, I don't see this in the official documentation. I noticed that the comparable figures, 3-1 and 3-3 in that documentation show different connections for a:

    Fig 3-1: USB Type_C UFP_D device shows SBU_1 w/AuxN connecting to the DisplayPort AUX_N, with a usb-c cable in line and

    Fig 3-3: USB Type_C UFP_D device shows SBU_1 w/AuxP connecting to the DisplayPort AUX_P.

      I don't see any programming registers inside of the Configuration that control this, so I'm wondering why switching from DFP_D to UFP_D changes the muxing inside of the TPS65982 from sending the SBU lines straight through to flipping them.
      As I said, I have control circuits that can flip the SBU lines, but I'm wondering if what I'm seeing is fixed, i.e. will it always operate this way, if in DFP_D mode the TPS65982 doesn't flip the lines, and if in UFP_D it flips the lines. If so, then I can at least determine how to control the mux.

    Thanks,
    WST