Pseudo Differential Receiver for Single-Ended Signaling Noise Immunity

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Solution Overview

Problem

In semiconductor chips, interconnect capacitance reduces signal integrity and transfer rate due to transmission line effects like distributed inductance, capacitance, and resistance, causing electrical interference and noise issues as operating voltage decreases.

Innovation Solution

Implementing on-die termination (ODT) with a termination resistor and sampling circuitry that uses a shared termination voltage to track common mode noise, eliminating the need for filtering circuitry and improving noise immunity by matching impedance and reconstructing input signals effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If single-ended signaling is used to reduce complexity, then device complexity is reduced, but signal integrity deteriorates due to noise and interference

Engineering Contradiction:

Improvereceiver complexityVSAvoidsignal integrity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

A pseudo-differential receiver is introduced as an intermediary component that converts single-ended signals into differential-like signals. The receiver uses a termination resistor connected to a reference voltage and a differential amplifier that compares the received signal against a inverted version of itself, effectively creating a differential processing mechanism that improves noise immunity while maintaining single-ended transmission simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The receiver changes the parameter of signal representation by converting the single-ended voltage signal into a differential voltage signal through the pseudo-differential circuitry. By using a differential amplifier with proper biasing and termination, the signal parameters are transformed to enable better noise rejection without requiring differential transmission lines.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If operating voltage is decreased to reduce power consumption, then energy usage is reduced, but noise margin deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidnoise margin

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent converts the harmful effect of low voltage (reduced noise margin) into a benefit by using the low-voltage differential signal to drive the pseudo-differential receiver. The differential processing mechanism amplifies the small voltage differences while rejecting common-mode noise, effectively turning the low-voltage limitation into an opportunity for improved noise immunity through differential signaling techniques.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The pseudo-differential receiver employs feedback mechanisms where the output of the differential amplifier is fed back through a resistor to create a virtual ground reference. This feedback loop stabilizes the operating point and enhances the effective noise margin by dynamically adjusting the reference levels based on the received signal conditions.

Inventive Principle:

Principle #23Feedback

3Speed

If interconnect capacitance is present in transmission lines, then signal transfer is enabled, but signal integrity deteriorates due to reflection and noise

Engineering Contradiction:

Improvesignal transfer rateVSAvoidsignal integrity

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The receiver is designed with preliminary termination resistance matching the characteristic impedance of the transmission line. This preliminary action of impedance matching prevents signal reflection before it can corrupt the received signal, allowing high-speed signal transfer while maintaining integrity. The termination resistor is positioned and valued to optimally absorb incoming signals without reflection.

Inventive Principle:

Principle #10Preliminary action

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 enhances signal integrity and transfer rates by reducing signal reflection and noise, maintaining signal quality across metal traces within and between dies in computing systems.

Implementation Method 1

Implementing on-die termination (ODT) with a termination resistor and sampling circuitry that uses a shared termination voltage

Methodology Applied

Scientific EffectImpedance matching: Electrical Impedance Tomography

Implementation Method 2

sampling circuitry that uses a shared termination voltage to track common mode noise, eliminating the need for filtering circuitry and improving noise immunity

Methodology Applied

Scientific EffectCommon mode noise tracking:

Data Source

PatentUS10749552B2Pseudo differential receiving mechanism for single-ended signaling

Publication Date: 2020.08.18 ADVANCED MICRO DEVICES INC

AI summary

Systems, apparatuses, and methods for performing efficient data transfer in a computing system are disclosed. A computing system includes multiple transmitters sending singled-ended data signals to multiple receivers. A termination voltage is generated and sent to the multiple receivers. The termination voltage is coupled to each of signal termination circuitry and signal sampling circuitry within each of the multiple receivers. Any change in the termination voltage affects the termination circuitry and affects comparisons performed by the sampling circuitry. Received signals are reconstructed at the receivers using the received signals, the signal termination circuitry and the signal sampling circuitry.