Designer’s Notebook

What to do when the trace doesn’t act as an “ideal” connection.

Read more: The Physics of Transmission Lines

A mismatch in trace symmetry can cause noise coupling or timing issues.

Read more: Signal Integrity Design Fundamentals

Ralf BrueningExact adaptations of impedance are often not necessary. Instead, minimize impedance deviations.

In part 1 last month, we took a back-to-basics approach and discussed line impedance and its effects on signal integrity. Every electrical conductor comprises capacitance, an inductance, and a frequency-dependent ohmic resistance. With increasing frequencies, these electrical characteristics will influence and distort the signal.

Applying a transmission line model based on the telegrapher’s equations (as typically common in signal integrity considerations, except for when considering extremely high data rates, e.g., Serdes channels), one often-used general expression for the characteristic impedance of a lossy transmission line is:
designersequation1Eq 1

Read more: Inside Signal Integrity: Impedance Control – Part 2

Ralf Bruening

The basics of line impedance influences.

Read more: Inside Signal Integrity: Impedance Control – Part 1

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