F-Tile Architecture and PMA and FEC Direct PHY IP User Guide

ID 683872
Date 11/04/2024
Public
Document Table of Contents

2.3.2.2.1. FGT Receiver Buffer and Equalizer

A simplified FGT eceive aalog fot ed is show i the followig figue.
Figue 47. Simplified RX Aalog Fot Ed
The vaious capacitos ad esistos fo the eceive aalog fot ed ae descibed below:
  1. You ca implemet o boad AC couplig capacitos, Co-boad, based o applicable stadads. Fo example, PCIe equies 176F to 265F o boad AC couplig capacitos.
  2. Co-chip, o-chip AC couplig capacito is 1pF. It is always o ad is oly bypassed i SDI mode. Thee is a equivalet 4 MΩ esisto afte the o-chip 1 pF AC couplig capacito, which ceates a cut-off fequecy:

    fc =1 / (2 * pi * RC) = ~40 kHz

  3. RDIFF-DC, DC diffeetial eceive impedace is pogammable to 85Ω o 100Ω, that is equivalet to 42.5Ω o 50Ω sigle eded.
  4. Whe you implemet o-boad AC couplig capacitos you must set VRX-CM-DC to goud temiatio. Whe it is DC coupled ad o o-boad AC couplig capacitos ae implemeted, VRX-CM-DC, eceive iput DC commo-mode voltage at the bumps must be:
    1. Smalle tha 700mV, if squelch detect is ot used.
    2. Must be betwee 200mV to 300mV, if squelch detect is used.
    Vcm is set to 700mV automatically if you use SDI mode.

The eceive buffe ad equalize fuctio the same fo FHT ad FGT PMAs. See FHT Receive Buffe ad Equalize fo details.