Source-Terminated Memory Channel Reflection Control With Timed Termination

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Solution Overview

Problem

Existing I/O circuits in integrated circuit devices face challenges in reducing unwanted reflections in source-terminated channels, particularly in low power memory systems where end terminations may be insufficient, leading to channel noise issues.

Innovation Solution

Implementing a termination control logic that enables source termination for a programmable time period after data transmission to absorb reflections, followed by disabling it for power savings, using either driver output impedance or explicit termination circuits, in memory systems like DDR and LPDDR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If end termination is used in low power memory systems, then power consumption is reduced, but unwanted reflections and channel noise increase

Engineering Contradiction:

Improvepower consumptionVSAvoidunwanted reflections

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The source termination is enabled before data transmission begins and remains active for a programmable time period after transmission completes. This preliminary and extended termination action ensures that reflections are absorbed during the entire signal propagation cycle, preventing channel noise while allowing end termination to be disabled for power savings.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The termination circuit transitions from a static always-on state to a dynamic state controlled by transmission events. The termination control logic dynamically enables the source termination based on transmission activity, maintaining it only when needed to absorb reflections, and disabling it during idle periods to reduce power consumption.

Inventive Principle:

Principle #15Dynamics

2Object-generated harmful factors

If source termination is continuously enabled, then unwanted reflections are reduced, but power consumption increases

Engineering Contradiction:

Improvechannel noiseVSAvoidpower consumption

Core Design Contradiction:

Object-generated harmful factorsVSUse of energy by moving object

Solution Approach 1:

Instead of continuous operation, the source termination is activated periodically based on transmission events. The termination control logic monitors transmission activity and enables the termination circuit only during and immediately after transmission periods, creating a periodic activation pattern that reduces power consumption while maintaining noise suppression effectiveness.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The termination is enabled in advance of potential reflection issues and maintained for a programmable time period after transmission completes. This ensures reflections are absorbed while allowing the system to disable termination during extended idle periods, balancing noise reduction with power savings.

Inventive Principle:

Principle #10Preliminary action

3Use of energy by moving object

If end termination is disabled for power savings, then power consumption decreases, but reflection absorption capability is insufficient

Engineering Contradiction:

Improvepower consumptionVSAvoidreflection absorption

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The termination function is segmented between two locations: source termination at the transmitting end and optional end termination at the receiving end. By enabling source termination dynamically based on transmission activity, the system achieves reliable reflection absorption without requiring continuous end termination, thus reducing power consumption while maintaining reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Source termination is enabled before and during transmission to proactively absorb reflections at the source end, compensating for the absence of end termination. This preliminary action at the source prevents reflections from propagating through the channel, maintaining reliability even when end termination is disabled for power savings.

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 effectively reduces channel noise below acceptable levels while minimizing power consumption by ensuring reflections are absorbed during the enabled termination period, applicable to various memory systems including low power and high-speed interfaces.

Implementation Method 1

to improve impedance matching between the I/O circuits and the communication links and reduce unwanted reflections

Methodology Applied

Scientific EffectImpedance matching: Electrical Resistance

Data Source

PatentUS9836428B2Reducing unwanted reflections in source-terminated channels

Publication Date: 2017.12.05 RAMBUS INC

AI summary

A memory controller and/or memory device control termination of a communication link in order to achieve power savings while reducing or eliminating unwanted reflections in the channel. Following transmission of data over the communication channel, termination is left enabled for a programmable time period beginning immediately following completion of the transmission. The time period is sufficiently long to allow the unwanted reflections to be absorbed by the termination. Following the time period, the termination is disabled for power savings.