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TUSB321AI: DIR pin is not changed even cable is reversed.

Chase Jeong
Mastermind 7445 points
Part Number: TUSB321AI
Other Parts Discussed in Thread: HD3SS3212, TPS22916

Dear TI experts,

My customer tests their own PCB with TUSB321AI.

the connection is as below.

[Sink;Scanner Device;USB C is controlled by ST MCU] <--USB C Cable--> [Source;Power Gender;USB C is controlled by TUSB321AI and HD3SS3212]

the problem is, when they flip the cable on sink side, CC1/CC2 voltage is normal and works well. but they flip the cable on source side, CC1/CC2 voltage is normal but DIR pin is always high.

if they connect source side on A, the voltage is as below;

CC1:1.77V, CC2:4.92V, DIR:3.35V

if they connect source side on B, the voltage is as below;

CC1:4.92V, CC2:1.77V, DIR:3.35V

related on this, I fould a thread below.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/722095/tusb321-tusb321-dir-output-does-not-toggle-when-the-plugged-usb-type-c-device-orientation-is-changed

this thread says that DIR pin change is also related to VBUS. but I cannot understand exactly. (VBUS is not just the input voltage? should we control it?)

I attach the waveform and schematic for your convenience. (schematic will be deleted after your support is done for my customer.)

scope.xlsx

0143.sch.pdf

And please let me know if you need more information about it.

Best regards,

Chase

  • +1
    TI__Mastermind 30130 points

    Hi Chase,

    As you saw in the linked E2E thread, as well as this E2E post, You should control VBUS with a VBUS switch.

    Chase Jeong said:
    VBUS is not just the input voltage?

    VBUS is more than just an input voltage, it is the power delivery mechanism between the host (DFP) and the device (UFP). DFP and DRP ports should control VBUS so that the CC negotiation happens before VBUS goes high. This can be done using the ID pin on the TUSB321AI by having VBUS applied when ID goes low.

    You can use the typical application in the 321 datasheet to see how a VBUS switch would look in your system (pictured below).

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Mastermind 7445 points

    Dear Shane,

    Thank you for your support.

    Please confirm that the sequence below is right or not ;

    1. CC pins connected detected

    2. ID pin goes to low (from high)

    3. VBUS applied

    And.. DIR pin would not go to low if VBUS voltage is applied before CC pins are connected. <- Is this right?

    Best regards,

    Chase

  • +1 in reply to Chase Jeong
    TI__Mastermind 30130 points

    Hi Chase,

    The sequence you've described is correct.

    I looked at your CC1/2 lines and don't see an issue. The 0 ohm resistors (R117/118) on these lines are ok.

    This leads me to believe the VBUS is your problem. We have seen cases in the past where the DIR pin does not respond to the cable flip when the VBUS is not controlled. 

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Mastermind 7445 points

    Dear Shane,

    Thank you for your support.

    My customer decided to add load switch to control VBUS. Please see the schematic below, and check that this is available.

    (maybe load switch is active low enable.)

    Best regards,

    Chase

  • +1 in reply to Chase Jeong
    TI__Mastermind 30130 points

    Hi Chase,

    You are on the right track.

    I am unsure what load switch you are using. If EN_L is a low-enable pin then the ID signal is connected correctly.

    Is the VBUS_DET line the same VBUS going to the connector? You should connect VBUS_DET on the 321 to the USB VBUS that goes to the connector.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Mastermind 7445 points

    Dear Shane,

    Thank you for your support, hope you had a good weekend.

    Yes, the input of load switch is from Type C connector, and the output is connected to VBUS_DET. and it is controlled by ID pin (VBUS_DET_EN).

    I suggested load switch TPS22916 which have active low enable to my customer.

    I will ask more if my customer have another question.

    Best regards,

    Chase