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TS5USBC400: Linking to TUSB2036 - series resistors needed?

Kevin Fleming
Prodigy 10 points
Part Number: TS5USBC400
Other Parts Discussed in Thread: TUSB2036

I have an application which will include two TUSB2036 hubs connected to PCs (upstream ports), and two connectors (USB A or USB C) for downstream peripherals. A microcontroller will decide which connectors will be connected to which hubs, so I am planning to put TS5USBC400 switches between them (with the 2-port side connected to the hubs and the 1-port side connected to the peripheral connectors).

For the DP/DM connections on the board (between the hub and switch ICs), are series resistors needed? The traces will be fairly short (approximately 1.5 inches, possibly shorter) and will be laid out as proper differential pairs with ground plane below and on the sides in order to maintain the 90 ohm impedance requirement for USB signaling.

In addition, the TS5USBC400 datasheet doesn't indicate what the series resistor values are needed for the sides of the switch which are connected off-board (to removable devices). What values should be used?

  • 0
    TI__Guru** 115825 points

    For the DP/DM connections on the board (between the hub and switch ICs), are series resistors needed?

    yes, TUSB2046 is FS hub, 22 0hm series resistor is needed on DP/DM, or you can use TUSB4041 which don't need external series resistor.

    Why do you need TS5USBC400 mux, for OVP?

    Regards

    Brian

  • 0 in reply to Brian Zhou
    Prodigy 10 points


    I've attached a very rough drawing of the design. The hosts will connect to one hub each, and the other side of the hubs will connect to a pair of devices, with a microcontroller deciding which devices will be connected to which hubs. The switches will be used to route each device connection to one hub or the other hub.

  • 0 in reply to Kevin Fleming
    TI__Guru** 115825 points

    Hi Kevin:

        The block diagram should work, but it's better is reset the Vbus to the USB connector every time you switch port.

    Regards

    Brian

  • 0 in reply to Brian Zhou
    Prodigy 10 points

    The device ports will be powered from the same power rail that powers the ICs, not by the Vbus from the host connectors, so that won't be an issue.

    Is it safe to assume that no series resistors are needed between the hub and switch ICs? What value of series resistors are needed between the switch ICs and the USB-A connectors (for the devices)?

  • 0 in reply to Kevin Fleming
    TI__Guru** 115825 points

    Maybe it's safe to use TUSB4020B, it didn't need external serial resistor.

    For TUSB2036, it did need 22-33 ohm serial resistor .

    Regards

    Brian