# Trace Length in PCB

• Trace on a PCB
• True transmission line
• It has both significant inductance and capacitance per unit length.
• Lumped inductance and capacitance are proportion to the length.
• Contributing Parameters for Delay
• Trace length. Usually, the rest of the parameters are preset.
• Trace width, thickness, shape
• Distance of trace from its reference plane
• Dielectric constant of the board material and/or coating
• Trace Length Effect on Rise/Fall Time
• Impedance looking into the trace
• Characteristic impedance Z0 (for an infinitely long trace)
• Load of receiver (for an infinitesimally short trace), usually much larger than the Z0
• For a finite length trace, the load that the driver sees will be somewhere between those two.