Electronic – 125 MHz parallel bus in a double 2.54mm header

connectordifferentialethernetfpgaheader

I have a BeMicro CV low cost dev board from Altera. It features a Cyclone V.

FYI: Schematics and gerber here

They routed impedance controlled differential lines to some dual 2.54mm standard headers.

See the at the top of the picture below:
enter image description here

It seems that they cared about the controlled impedance, and also the line lengths.

I would like to connect a 1000Mbit PHY with GMII interface (parallel 125MHz clock).

Can I plug a daughter board to this one and convey the 125MHz signals using a simple 2.45mm header?

Best Answer

I think it should work. These connectors seem to have relatively low capacitance.

If you are really worry about this - you may try to pass 125MHz or even faster signal from lab generator and see what is going on oscilloscope.

These connectors were used for ATA hard disks, and they were working with pretty long ribbon wire with bus speed up to 33MHz, so without that ribbon cable there should be no problem with 125MHz (or 125MHz differential signal).

ata bus frequency

Source:

Upgrading and Repairing PCs Scott Mueller

http://books.google.com/books?id=E1p2FDL7P5QC

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