Impedance and Routing

The following points should be taken in to account during the PCB design phase:

• The E-bus traces have to be routed in inner layers.
• The differential impedance of the LVDS traces shall be 100 Ω.
• Width and spacing of the differential signal are depending on the concrete layer stack up and have to be calculated individually.
• The differential signals should be routed as edge coupled traces.
• The distance between the differential pairs should be three times larger than their inner distance (see following Figure (D)).
• No GND area may form between the differential lines (D). This usually results from the required impedance.
• Differential pairs should be routed without Vias (vertical interconnect access), in order to avoid impedance jumps.
• Maximum values for uncoupled trace and overall trace length can be found in the specification for LVDS signals ANSI/TIA/EIA-644 „Electrical Characteristics of Low Voltage Differential Signaling (LVDS)