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Original question:

TUSB522P: Hardware related design issues.

TUSB522P: How to evaluate whether the TUSB522P de-emphasis dB can meet the loss requirements?

shunda zhong
Prodigy 30 points
Part Number: TUSB522P

Hello, there is a question to ask as follow:

The USB 3.1 link loss file indicates that the DEVICE->hoST link has a maximum insertion loss of -20dB

Follow the model: green indicates HOST loss10dB, brick red indicates cable loss of 3.5dB/m, and blue indicates DEVICE loss6.5dB

If I now use a 1m cable just enough to meet -20dB, if I choose Rederiver to emphasize the chip to -7dB, does that mean I can use a 3m cable?
Because the de-emphasis -7dB just compensates for the insertion loss of the 2m cable, can it be understood in this way?

  • 0
    TI__Guru**** 176811 points

    Hi,

    One clarification is on the cable 3.5dB insertion loss. The USB ECN reduced the loss allocation to 3.5dB for cables that use the microB connector, effectively limiting them to 1m or less. It is not 3.5dB/m loss.

    If you place the TUSB522P inside the cable, then you can increase the cable length, effectively making the passive cable into an active cable.

    Thanks

    David