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PCIe differential impedance

milos.stankovic , 09-02-2022, 02:10 AM
Hi everyone!

I tried to check why PCIe data differential signals have 90Ohm differential impedance and clk 100Ohm. In IMX6DQ6SDLHDG.pdf there is a guidline that says differential impedance should be 85Ohm +/- 10% for differential pairs (page 61/128). I suppose that is why RX and TX have 90Ohm impedance (it falls within 85Ohm+/-10%). I see no mention of clk diff pair have 100Ohm impedance in either IMX6DQ6SDLHDG.pdf or Freescale design guide (http://www.freescale.com/files/train...IGN_PCI_SMGIII
I saw in one of the Robert's responses reference to https://www.renesas.com/eu/en/docume...ign-guidelines
it recommends 100Ohm for Clk, Rx and Tx.

robertferanec , 09-02-2022, 04:52 AM
Hi @milos.stankovic, is there a question?
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