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SN75LVPE802: Trace length requirement

Antony Lin
Genius 13480 points
Part Number: SN75LVPE802
Other Parts Discussed in Thread: DS125BR111, DS80PCI102

Hi,

To support PCIE-GEN3, what kind of pre-channel and post-channel trace length SN75LVPE802 can support?  Any minimum/maximum requirement?

Thanks!

Antony

  • 0
    TI__Mastermind 43795 points

    Antony,

    I would not recommend the SN75LVPE802 for PCIe at this time.  The latest PCIe system devices do not always detect the LVPE802 input termination, even with the external pull-down resistors.

    Instead I recommend the DS80PCI102 or DS125BR111 to solve PCIe 1-lane signal conditioning challanges.  Both DS125BR111 and DS80PCi102 will extend the PCIe specification by ~ 10dB.  In most systems this works out to approximately a 30dB attenuation at 4 GHz.  There are many variables which contribute to attenuation, but typically this is equal to ~ 30 inches of total PCB trace at PCIe Gen3.

    The DS80PCI102 should be placed close to the center of the channel.

    The DS125BR111 offers more placement flexibility.  It can be placed anywhere on the channel as long as the minimum attenuation to the closest PCIe Tx pins is 8 dB.

    Regards,

    Lee