6
\$\begingroup\$

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?

\$\endgroup\$
5
\$\begingroup\$

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?

\$\endgroup\$
  • \$\begingroup\$ Could you elaborate on what you mean by "long edge away from PCB"? \$\endgroup\$ – Funkyguy Jan 9 '15 at 20:07
  • \$\begingroup\$ @Funkyguy I've added a couple of links to example datasheets. \$\endgroup\$ – markt Jan 10 '15 at 3:33
  • \$\begingroup\$ Ahhhh well played! I didn't even think about that. Thanks! \$\endgroup\$ – Funkyguy Jan 10 '15 at 3:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.