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TPS65982 / AMSEL control

K.Yaita
Guru 29720 points
Other Parts Discussed in Thread: HD3SS460, TPS65982, TPS6598X-CONFIG

Hi Team,

My customer considers to use TPS65982+HD3SS460 to support alternate mode (Display port).

If I select "DisplayPort PIN ASSIGNMENT" C/D/E in application customization tool, how does TPS65982 decide the state of AMSEL?
(How does TPS65982 decide "4 Lane" or "2 Lane and USB3.1"?)



Best Regards,
Yaita / Japan disty

  • 0
    TI__Mastermind 30310 points

    Yaita-san,

    Please refer to Table 1 of the HD3SS460 specification.

    The EN, POL, and AMSEL GPIO Events are designed to match the truth table in Table 1 of the HD3SS460 datasheet.

    AMSEL is the only one of these 3 Events that can be tri-stated to get an "M", or Mid-rail Voltage, value in the Table. This will require equal pull-up & pull-down resistors externally or you can enable both of the internal 100k-Ohm pull-up & pull-down resistors of the TPS65982 in the TPS6598X-CONFIG Config Tool.

    EN and POL of the TPS65982 can only be "H" for High (1) or "L" for Low (0).

  • 0 in reply to Brian Berner
    Guru 29720 points

    Hi Brian-san,

    Thank you for your reply.
    Yes, I already refer to Table 1 of the HD3SS460 datasheet.

    If I set DFP_D and DisplayPort PIN ASSIGNMENT C/D/E as the following, I think it could support both "4 Lane" and "2 Lane and USB3.1".
    I believe TPS65982 sets the state of AMSEL but couldn't catch how does TPS65982 decide the state of AMSEL. Is there any flow chart to decide the state of AMSEL?




    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29720 points

    May I Have your comment?
    If there is anything unclear, please let me know.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 30310 points

    Yaita-san,

    Is your product the UFP_D or DFP_D for DisplayPort:

    • DFP_D = DisplayPort Source, usually also the DFP_U for USB PD (or Host, using USB2/3 terminology)
      • Laptops and Tablets are common example of DFP_D products
    • UFP_D = DisplayPort Source, usually also the DFP_U for USB PD (or Host, using USB2/3 terminology)
      • Monitors and Docks are common example of  UFP_D products

    ?

    The simple answer is the DFP_D has the authority to make the decision, but the UFP_D is allowed to have a preference. In my experience, if a DFP_D supports both 2- and 4-Lane operation, it will follow the preference of the DFP_D.

    If your product is the DFP_D, as shown in your TPS6598X-CONFIG Tool screenshot, and both the DFP_D and UFP_D support both Pin assignments 'C' and 'D', then the DFP_D will rely on the value of the "Multi-Function Preferred" bit to determine which Pin Assignment is selected:

    • Mult-Func Preferred = 1 = 2-Lanes USB3 + 2-Lanes DP (Packet #35 below from UFP_D)
      • Pin Assignment 'D' Selected (Packet #37 below from DFP_D)
      • TPS65982 GPIO Event Result: AMSEL = L = '0' 

    • Multi-Func NOT Preferred = 0 = 4-Lanes DP for 4K resolution (Packet # 81 below from UFP_D)
      • Pin assignment 'C' Selected (Packet # 83 below from DFP_D)
      • TPS65982 GPIO Event Result: AMSEL = H = '1' 

    In my experience, the Google Type-C to DP adapter dongle is the best example of a product using Pin Assignment 'E' for 4-Lane operation. In this case, AMSEL = H = '1' also.