Signal Integrity and Power Integrity

Signal Integrity

Basic Concepts

Signal Integrity (SI) is the measure of the quality of an electrical signal. In high-speed digital and analog circuits, maintaining signal integrity is crucial for reliable operation.

What is Signal Integrity

Signal Integrity involves ensuring that electrical signals are transmitted from source to destination without undue degradation.

Transmission Lines

Transmission lines are conductive pathways for distributing electrical signals. They can be microstrip or stripline configurations on a PCB or coaxial cables.


Crosstalk is the unwanted coupling of one circuit's signals into another circuit, causing noise and interference.

Differential Pairs

Differential pairs are pairs of conductors used to carry differential signals, which helps to improve signal integrity by canceling out common-mode noise.

Vias and Impairments

Vias are conductive holes on a PCB used to route signals from one layer to another. They can introduce impedance mismatches and other impairments.


Termination involves adding resistors at the end of transmission lines to reduce reflections and improve signal quality.


Timing aspects like setup and hold times, clock-to-q delays, are crucial for the functioning of high-speed digital circuits.

Application Examples

DDR Memory Interface

Double Data Rate (DDR) interfaces are common in memory systems and require stringent signal integrity due to high-speed operation.

High-Speed Serial Interface

Interfaces like USB, HDMI, and Ethernet require careful design to maintain signal integrity.

Power Integrity

Basic Concepts

Power Integrity (PI) is the discipline of designing and maintaining the electrical power delivery system from the source to the load.

What is Power Integrity

Power Integrity ensures that all electronic components in a system receive stable and clean power.

DC Current and Voltage

In PI, it's crucial to maintain stable DC current and voltage levels across all components.


Decoupling involves using capacitors to filter out high-frequency noise from the power supply.

Transient Performance

Transient performance refers to how quickly the power delivery system can respond to sudden changes in load current or voltage.

Application Examples

DC (IR) Voltage Drop

This involves analyzing how much voltage is lost as current moves through conductive pathways, affecting component performance.

Decoupling and Noise

Decoupling capacitors are used to reduce power supply noise, which is vital for the functioning of sensitive components like CPUs and FPGAs.