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TUSB1104: For active USB Type-C cable

Part Number: TUSB1104
Other Parts Discussed in Thread: TUSB1002A, TUSB1044

Hello everyone,

our plan is to do an active USB Type-C cable which supports speed up to USB 3.2 Gen 2x2 (20 Gbits) and also use the e-Marker CYPD2105-20FNXIT from Cypress.

I found the TUSB1104 which is a USB 3.2 x2 Adaptive Linear Redriver. However in the datasheet there seems to be no information if the TUSB1104 can be used for active cables.

So is it possible to use the TUSB1104 in active cables?

If so should there be one TUSB1104 per cable or is it necessary to use one per plug? Are there any requirements for the e-Marker?

In the data sheet of TUSB1104 on page 43 I can only see that there is a connection from SCL, SDA and EN between the TUSB1104 and the CC/PD controller. Is this connection necassary?

Are there any reference designs/design rules for active cable design with the TUSB1104?

Thanks for your help

Tobi

  • Hi Tobi,

    Active cable is not an intended application for the 1104. Like you noticed, this re-driver does not include active cable support in the datasheet, and was not designed with this use case in mind.

    The amount of power supplied by VCONN in your system would likely be the limiting factor. The 1104 has an average power draw of 550mW, which could be too high for VCONN to supply depending on the implementation.

    An example of a re-driver designed for active cables would be the TUSB1002A, which has a comparatively lower power draw of 340mW. However, this device only supports up to 10G data rates

    Best,

    Shane

  • Hi Tobi,

    I see that my answer did not resolve your question. Can you elaborate on what you would like to know that I missed in my response?

    Best,

    Shane

  • Hi Shane,

    Thank you very much for your help. Sorry to ask again, but are you sure that this will be a problem?

    The TUSB1044 also has a power consumption of 578 mW and can be used in active cables, according to the document 'USB Redriver and Type-C Solutions' by Zhihong Lin. I checked the USB Type-C Cable and Connector Specification for VCONN and it says that Vconn can achieve a power of 1 watt. Will it be a problem because I have to use 2 Redrivers so 2 *550 mW > 1000 mW?
    Thanks for the suggestion of TUSB1002A, but it only has inputs for one Tx and one Rx pair. So I would have to use 2 per plug?
    The TUSB1044 has 4 channels, which is what I need. It can handle a data rate of USB 3.1 Gen2, which is 10 Gbps. So 5 Gbps per channel, right?

    Thank you

    Tobi

  • Hi Tobi,

    It is possible for the 1044 or 1104 to be used in an active cable application, however it depends on your implementation. As you noticed, since VCONN can only support 1W, you could not use the 1104 or 1044 on both sides of the cable. You could try using one 1104 somewhere in the middle, but make sure to keep the total power in the cable within the 1W allowed by VCONN. 

    Generally an active cable would have other power drawing elements besides the re-driver (PD controller, voltage regulators). These elements all factor in to the power budget. The concern I have with using a re-driver like the 1104 is that you may not have enough power left over for the other devices in your cable. Do you know what other power drawing elements would be in your cable?

    If you do decide this re-driver, note that AEQ should be disabled

    Best,

    Shane

  • Hi Tobi,

    Looking through the USB spec, I noticed the maximum power consumption on VCONN would be 1.5W for a dual lane application.

    This should help the power budget for your cable. From what I can gather, the power drawing components in an active cable are the re-driver(s), the e-marker, and any voltage regulators or PD controllers used to power these devices.

    Since the 1104 draws 550mW, I believe it would be possible to use one on each side of the cable. This would leave you with 400mW for other cable elements.

    A linear re-driver like the 1104 is only able to compensate for loss on the receiver side. I drew a simple diagram on how each signal channel would be compensated in an application using two 1104 re-drivers.

    I hope this helps, feel free to follow up with any more questions if I missed anything.

    Best,

    Shane

  • Hi Shane,

    thank you very much for answering my question. I just have two more questions.

    1. If I use the TUSB1104 and configure it via pin-strap. Is the connection between PD-Controller and Redriver via SCL and SDA necessary or can I leave the pins open?
    2. The TUSB1044 has 4 channels. In the datasheet it says it supports USB 3.1 Gen 2. Does this meas it supports 10 Gbps per Rx/Tx pair so 20 Gbps in total or in total 10 Gbps?

    Best regards,

    Tobi

  • Tobi

    1. If I use the TUSB1104 and configure it via pin-strap. Is the connection between PD-Controller and Redriver via SCL and SDA necessary or can I leave the pins open?

    Yes, you would still want to use the PD controller to control TUSB1104 using its FLIP, CTL0, and CTL1 pin in the pin-strap mode.


    2. The TUSB1044 has 4 channels. In the datasheet it says it supports USB 3.1 Gen 2. Does this meas it supports 10 Gbps per Rx/Tx pair so 20 Gbps in total or in total 10 Gbps?

    10G per lane, so total is 20G.

    Thanks

    David

  • Hi David,

    since the TUSB1044 is capable of transmitting 20G would it be more suitable for acitve USB-C Cables which support USB 3.2 Gen2x2 than the TUSB1104? Since the TUSB1104 has features like AEQ which should not be used in active cable applications and would be not necessary.What is your opinion on this?

    Why should there be a minimum distance between AC capacitor and TUSB1104 (0.4 inches)?

    The function of the EN pin is still not entirely clear to me. Can it be set to high all the time in an active cable?

    Can I dm you for more questions? Thank you very much for your help.

    Best regards,

    Tobias

  • Hi Tobi,

    David had filled in for me over the holiday. I see you are curious between using the 1104 or the 1044 for USB 3.2x2

    The 1044 does not have support for USB 3.2x2 mode, so I would recommend using the 1104 even without the need for AEQ. The 1044 can do USB 3.1 and has support for DP alt mode, however it does not contain the configuration mode necessary for USB 3.2 x 2.

    Why should there be a minimum distance between AC capacitor and TUSB1104 (0.4 inches)?

    The parameters in this table are specific to the design example presented. They are not a hard requirement and should only be used as a reference.

    In general, leaving some space between the re-driver and AC capacitors can help lower the intensity of signal reflections caused by the capacitors. In this example 0.4in was used but this would be up to your discretion.

    The function of the EN pin is still not entirely clear to me. Can it be set to high all the time in an active cable?

    The EN pin should be pulled up for normal operation of the device.

    When powering on, make sure the EN pin is held low for 5ms after VCC is stable.

    Here is a diagram in the datasheet showing how that would look:

    After the device is powered-up, you could have EN set high constantly as you mentioned.

    If you need support that cannot be included on this public thread, you can send me a friend request through E2E and it will let us direct message.

    Best,

    Shane