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Original question:

TUSB522P: Board Configuration

TUSB522P: Difference between a redriver and a repeater

Arron Danehy
Prodigy 50 points
Part Number: TUSB522P


Tool/software:

I am working on an application with adding active components on a custom board to maintain a strong signal over 7m. Currently I was thinking about using the TUSB522P redriver because I am using aUSB3.2 Type A connector. However, I was curious if I should be using a repeater instead and what the advantages may be with one or the other. Does one keep signal strength over a longer distance? Is it possible to determine the distance the signals can maintain strength from the spec sheet? If there are multiple cables with multiple redrivers/repeaters would they create more errors in the system or increase the bit-error rate?

  • +1
    TI__Mastermind 32585 points

    Hi Arron,

    'Repeater' is a broad term that can mean either a re-driver or a re-timer. Please see this E2E FAQ for a description of the differences between these two.

    Arron Danehy said:
    Is it possible to determine the distance the signals can maintain strength from the spec sheet?

    The spec sheet of a re-driver will only give you the dB loss that can be compensated. You need to consider the loss of the trace/cable material as well if you want to find a good length.

    For example, you could have a long cable with high quality (low loss) material that could extend multiple meters and be ok. On the other hand, you could have a high loss cable that fails at the same length. Its a good idea to find the loss of your cable in dB before designing in a re-driver to ensure there is enough EQ and DE to cover the channel loss.

    Arron Danehy said:
    If there are multiple cables with multiple redrivers/repeaters would they create more errors in the system or increase the bit-error rate?

    The short answer is yes. Each re-driver in the signal path will add a small amount of jitter to your signal. If you cascade multiple redrivers, the added jitter could be enough to create errors as you describe. Jitter is not something a re-driver can fix and must be kept to a minimum to ensure the USB port passes compliance. An alternative to consider is using a re-timer, which does have the ability to clean up jitter in the USB signal.

    Let me know if you have any questions.

    Best,

    Shane