Integrated AC Coupling Capacitors for PCIe Signal Transmission

Solution Overview

Problem

Conventional Peripheral Component Interconnect Express (PCIe) designs require numerous off-chip discrete capacitors for AC coupling, consuming space on printed circuit boards (PCBs) and limiting their size and functionality due to the need for bidirectional communication, which also complicates noise attenuation and impedance matching.

Innovation Solution

Integrating capacitive elements within the transmitting integrated circuit (IC) to function as AC coupling capacitors, eliminating the need for off-chip discrete components and allowing for efficient capacitively coupling signals between ICs, thereby reducing PCB size and enabling more compact designs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If off-chip discrete capacitors are used for AC coupling in PCIe designs, then signal coupling and noise attenuation are achieved, but PCB space is consumed and device complexity increases

Engineering Contradiction:

Improvesignal couplingVSAvoidPCB space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent integrates AC coupling capacitors directly into the transmitter IC chip, merging the capacitor function with the existing transmitter circuitry. This eliminates the need for separate off-chip discrete capacitors, thereby reducing PCB space while maintaining the necessary AC coupling functionality for differential signal transmission.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated capacitive elements serve multiple functions: they provide AC coupling for differential signals, enable impedance matching, and contribute to noise attenuation. By making the transmitter IC multi-functional, the design eliminates separate components without compromising signal integrity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If off-chip discrete capacitors are used for AC coupling, then bidirectional communication is enabled, but the number of components increases and manual replacement becomes necessary

Engineering Contradiction:

Improvebidirectional communicationVSAvoidnumber of components

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent integrates AC coupling capacitors directly into the transmitter IC chip, merging the capacitor function with the existing transmitter circuitry. This eliminates the need for separate off-chip discrete capacitors, thereby reducing PCB space while maintaining the necessary AC coupling functionality for differential signal transmission.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The integrated capacitive elements are built-in and require no manual installation or replacement. The transmitter IC is self-sufficient, providing all necessary AC coupling functionality internally, which eliminates maintenance overhead and reduces device complexity.

Inventive Principle:

Principle #25Self-service

3Area of stationary object

If integrated capacitive elements are used within the IC, then PCB space is reduced and trace routing is simplified, but manufacturing precision requirements increase

Engineering Contradiction:

ImprovePCB spaceVSAvoidintegration precision

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent integrates AC coupling capacitors directly into the transmitter IC chip, merging the capacitor function with the existing transmitter circuitry. This eliminates the need for separate off-chip discrete capacitors, thereby reducing PCB space while maintaining the necessary AC coupling functionality for differential signal transmission.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent specifies capacitance values in the range of 0.1 pF to 10 pF for the integrated capacitive elements. By optimizing these parameter specifications, the design achieves effective AC coupling with integrated structures, balancing manufacturing feasibility with performance requirements.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach reduces PCB size, minimizes the need for manual replacement of defective capacitors, and enhances signal integrity by integrating low-capacitance capacitive elements within the IC, freeing up space for other components and simplifying trace routing, while maintaining effective noise attenuation and impedance control.

Implementation Method 1

a capacitive element, such as an integrated coupling capacitor, integrated within the IC and coupled to the transmitting component

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS8432019B2Techniques for capacitively coupling signals with an integrated circuit

Publication Date: 2013.04.30 NVIDIA CORP

AI summary

System and apparatus for capacitively coupling signals with an integrated circuit (IC) are described. Capacitive elements disposed with a transmitting IC effectively function as AC coupling capacitors for a PCIe, DisplayPort™ or other interconnect linking the transmitting IC with a receiver disposed remote there from. Integrating the coupling capacitors allows for a smaller and more economical design for the circuits that utilize the interconnect.