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TUSB212: question about TUSB212

chris Gu
Intellectual 920 points
Part Number: TUSB212


Tool/software:

Hi teams,

My customer, LANGO, is using the TUSB212RWBR. They've installed pull-up resistors RU32 = 47K and pull-down resistors RU36 = 47K. I suspect this will cause the chip's DCBOOST/ENA_HS to malfunction. However, several hundred boards have already been shipped to the end customer, and removing components is prohibited, so removing the pull-up resistors is not an option. Is it possible that the redriver won't work with the current configuration? Can adding pull-up resistors (e.g., 1M) resolve this issue? Are there other solutions to resolve this issue without removing components?

Best Regards

Chris

  • 0
    TI__Mastermind 43640 points

    Hi Chris,

    Is the customer seeing issues with the TUSB212 already, or are you just concerned ahead of it being implemented? Is the pull-up resistor populated or not?

    With both 47KOhm resistors populated, the 3.3V rail should divide down to 1.65V, which will set the DC_BOOST pin to medium, which is okay. If the pull-up isn't populated and just pulled-down to ground, then DC_BOOST will be set to low, which is also okay. My main concern is the values of the capacitors being used for the VCC and VREG pin. It looks like they are using 100pF, when we recommend 100nF or 1uF: 

    Thanks,

    Ryan

  • 0 in reply to Ryan Kitto
    TI__Intellectual 920 points

    Hi Ryan,

    The customer connected both resistors in the current project. This triggers Full Speed ​​(FS) Mode. If the RU32 is not connected as the customer previously did, Low Speed ​​(LS) Mode will be triggered. Maybe there are some problems with my understanding, but I really want to confirm again whether connecting two resistors at the same time is not risky for customers? In addition, I am very grateful for your reminder. I will suggest customers to modify the capacitor size.

    Best Regards

    Chris

  • +1 in reply to chris Gu
    TI__Mastermind 43640 points

    Hi Chris,

    chris Gu said:
    The customer connected both resistors in the current project. This triggers Full Speed ​​(FS) Mode. If the RU32 is not connected as the customer previously did, Low Speed ​​(LS) Mode will be triggered.

    The ENA_HS pin does not actually control the mode of the TUSB212. This pin has two functionalities, DC_BOOST, which acts as a input, and ENA_HS, which acts as an output.

    At start-up, the pin acts as DC_BOOST, sampling what the input voltage of the pin is to determine what the level of DC_BOOST is set as. After start-up, the pin functionality switched to ENA_HS, which is an output pin for debug. This pin will indicate when the TUSB212 detects a HS signal on the DP/DM lanes, with a low output indicating there is no HS signal, so the redriver is not enabled, while a high output indicates that there is a HS signal, and the redriver is enabled, boosting the signal as it moves beneath the redriver.

    The redriver does not have a LS or FS mode, and only enables when it detects a HS signal on the DP/DM lanes. With the current configuration, I don't see any issues. I have not seen this design before as far as I am aware, has the customer already performed USB2 compliance testing, I.E eye diagrams?

    Thanks,

    Ryan