Signal Integrity

LVDS Signals  |  FPGA differential signalling  |  PCB Layout

In the transmission of high speed signals transmission line effects need to be taken into consideration and quantified.  ELMG Digital Power high speed transmission systems use LVDS signalling to connect across PCBAs and through cables.

In this fiber optic communication link the signal transfer from the microprocessor to the ELMG Digital Power PowerComms link is via LVDS.

PCB layout with top layer 100 ohm LVDS differential transmission lines

In order to use low cost four layer boards the 100 Ohm natural impedance transmission line for the LVDS is fabricated on the topside of the PCB.  The differential pair tracks have lengths matched to minimise crosstalk and signal reflections.  The signal travels across the board between the Xilinx six series FPGA and to an impedance matched cable and connector.

A LVDS to single sided signal converter PCBA board is plugged in on the microprocessor controller board.  This completes the LVDS link.

This system allows high speed high fidelity communication between the fibre communication link FPGA and the microprocessor.  It provides a simple high speed, highly noise immune, communication hardware physical layer

PCBA showing layout of the LVDS transmission lines