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Given a fairly common smd style usb type C receptacle connector, such as the following: TYPE-C-31-M-12

Two pairs of D+/D- signals are provided, due to the double sided nature of the type c connector. Usually, these are routed as a differential pair to the destination - however, as in the given example, there's two pairs of D+/D- and only one pair of destination pins.

What is the best practice in this scenario? Should the two pairs of digital pins be joined, then routed differentially to the destination?

If the connector is just being used for USB/USB2.0 communications, is routing of the second pair necessary at all? In that case, should those pins be NC, pulled to some potential or otherwise?

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  • \$\begingroup\$ There are many application notes from different manufacturers of USB devices which describe best practices how to route USB signals, including how to work with USB-C connector. Have you read any of them, because you are asking quite general question which would take a few pages to answer thoroughly. \$\endgroup\$
    – Justme
    Aug 9 '21 at 7:01
  • \$\begingroup\$ It was intended to be a general question, with no specific application in mind. Another wording could be: USB type a, b, micro and mini feature one pair of D+/D- pins, while usb type c features 2 pairs - what should be done with the 'second' pair, and how should they be routed? \$\endgroup\$
    – nuggetbram
    Aug 9 '21 at 12:07
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You route a single differential pair between connector and chip as usual.

At the connector, you connect the differential pair to both sets of pins on the receptacle, as the plug only provides a single set of pins. The connecting stubs should not exceed 3.5 mm.

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What is the best practice in this scenario? Should the two pairs of digital pins be joined, then routed differentially to the destination?

Yes, that's what all people do. Join the proper pins in a shortest available way at the connector/receptacle, and route the result as a differential transmission line. Connecting the "second pair" is a must, otherwise the cable will work only in one way, but not in flipped way.

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