Electronic – Mini USB receptacle versus proper PCB layout


While routing my CY7C68013A based PCB I just realized that regular USB B receptacle and mini USB equivalent have D+ and D- effectively swapped.

It seems that the chip was prepared for regular size receptacle (DP is on the left if looking towards the chip), while for mini USB I have to route one of the tracks under the receptacle.

Is it really like this, or did I mess something up? How am I suppose to keep the tracks impedance and length constraints, while one of the tracks needs to go a different way, around the receptacle pads?

Best Answer

I've noticed the same problem when routing boards with the FTDI FT232 chips. Here's what the CY7C68013A datasheet says about routing those signals:

  • DPLUS and DMINUS trace lengths should be kept to within 2 mm of each other in length, with preferred length of 20 to 30 mm.
  • Maintain a solid ground plane under the DPLUS and DMINUS traces. Do not allow the plane to split under these traces.
  • Do not place vias on the DPLUS or DMINUS trace routing.
  • Isolate the DPLUS and DMINUS traces from all other signal traces by no less than 10 mm.

I would suggest the zig-zag method, but only if it that little detour around the pin added more than 2 mm to the trace length.