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PCIe line impedance

Question asked by Dominic Musgrove-Wethey on Jul 15, 2016
Latest reply on Jul 15, 2016 by igorpadykov

Hi

 

I am using PCIe to communicate between an IMX6 and IGLOO2 FPGA, both mounted on the same PCB.

The IMX6 hardware development manual says to route PICe at 85 ohms differential impedance, yet the SABRE_SD evaluation board, IMX6 REX and other designs I have seen all route PCIe lines at 100 ohm differential.

 

The IGLOO2 can terminate to 80, 100 or 120 ohm differential, should I use 85 or 100 ohm impedance lines?

Can anyone explain why the hardware development guide says 85 ohms yet everyone else seems to use 100 ohm lines?

 

 

Regards,

Dominic

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