The impact of driver impedance upon transmission line impedance

The principle feature of robust design for quality is parameter design: selecting the design parameters to minimize quality loss. The tolerance in interconnection characteristic impedance (Zo) can impact the cost of a printed circuit board (PCB), multichip module (MCM), or hybrid if the tolerance is too small and the cost of the interconnect has to absorb rejected parts. This paper extends a theory of controlled impedance design that is compatible with the principles of robust design for quality. Practical applications and broad implications of this theory are demonstrated. The results are pertinent to both designers and fabricators of interconnections for high speed digital systems. Designers of digital output drivers will see the effect of driver impedance upon transmission line impedance.<>