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So I've been looking around for quite some time for a USB<->UART transceiver that has the pins properly ordered.

If you'll look at the picture here, you can see that the pin order of the connector is

  1. VBUS
  2. D-
  3. D+
  4. GND

and the pins at on the bridge are swapped which means I have a problem with laying out the USB signals should both the connector and the IC be on the top layer.

enter image description here

Pulled from the CP2103 datasheet

I've tried with the FT234xd and other various bridges but I run into the same layout issue like below where the signals cross which becomes a problem.

enter image description here FT234xd without the resistors in between the signal and the bridge.

Of course I could turn the bridge around and have the pair be run non-parallel down the length of the bridge although I feel like that would be less than ideal.

In the end I'm left wondering is there a good reason for this or am I missing something entirely related to the layout of a USB transceiver?

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1 Answer 1

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There are (in this context) two types of USB Micro-B connector; I tend to think of them as "long edge close to the PCB" and "long edge away from the PCB". You're using the "long edge close to the PCB" kind. Use the other kind and the order of the pins flips.

Unfortunately there doesn't seem to be a search term (for Digikey or Element14, at least) that can be used to discriminate between the two types, so you have to check the datasheets individually.

Here are two example datasheets, the TE2013499-1 and the Molex 475900001 (the latter is actually an AB but that changes nothing). Notice how the insertion orientation of the micro-B plug is inverted with respect to each other?

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  • \$\begingroup\$ Could you elaborate on what you mean by "long edge away from PCB"? \$\endgroup\$
    – Funkyguy
    Commented Jan 9, 2015 at 20:07
  • \$\begingroup\$ @Funkyguy I've added a couple of links to example datasheets. \$\endgroup\$
    – markt
    Commented Jan 10, 2015 at 3:33
  • \$\begingroup\$ Ahhhh well played! I didn't even think about that. Thanks! \$\endgroup\$
    – Funkyguy
    Commented Jan 10, 2015 at 3:44

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