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AC coupling location in PCIe lanes on Keystone I devices

Thomas Yang55737
Expert 5056 points

Hi

In Keystone II serdes design guide, , it recommends that the AC-coupling capacitors should be close to the transmitter end and not the receiver end on PCIe lane, also in PCIe spec, it requires this. But in Keystone I serdes design guide, it doesn't mention this point. My question is: does AC-coupling capacitor also need put in the transmitter end in Keystone I devices? C6655 EVM schematic also doesn't put AC-coupling in transimtter side, is this correct? or any special reason on this

Thanks

Thomas

  • 0
    TI__Guru* 81335 points
    Thomas,
    The Hardware Design Guide for KeyStone I Devices, especially section "4.3.3 PCIe Net Classes & Specific Rules" to see if your design meets all the routing requirements for PCIe. And PCI Express requires AC coupling capacitors be placed in close proximity to the transmitter on each Lane's differential signal pair as mentioned in the PCIe standard specification.
    Please refer below threads,
    http://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/p/252585/884134#884134
    http://e2e.ti.com/support/dsp/c6000_multi-core_dsps/f/639/t/160105
  • 0
    TI__Mastermind 43660 points
    Hello Thomas,

    The PCIe specifications are common for all devices and it is necessary to provide AC coupling caps on transmit side.

    Regards,
    Senthil