Bidirectional IO Buffer With Shared Impedance for Mode Switching

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Solution Overview

Problem

Conventional high-speed IO buffers require separate design for driving and receiving modes, resulting in larger area and reduced flexibility due to different impedance and linearity requirements, making them less adaptable to various applications.

Innovation Solution

A bi-directional IO buffer design where the driver and receiver share impedance in both modes, utilizing a circuitry that selects between driving and receiving modes by controlling switch elements and resistive elements to achieve efficient impedance sharing, reducing the overall area and maintaining impedance linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If separate design is used for driving and receiving modes, then impedance and linearity requirements are met, but area increases and flexibility decreases

Engineering Contradiction:

Improveimpedance and linearity requirementsVSAvoidIO buffer area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent merges the driving and receiving modes by sharing the impedance network between them. The same resistive elements and switch elements are used in both modes, eliminating the need for separate impedance circuits. This combining approach reduces the overall area while maintaining the required impedance characteristics for both driving and receiving operations.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The impedance network is designed to serve multiple functions: it provides the required impedance for driving mode, the required impedance for receiving mode, and can be dynamically reconfigured between modes using switch elements. This multi-functionality allows a single circuit to replace what would traditionally require separate dedicated circuits for each mode.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If separate design is used for driving and receiving modes, then mode-specific requirements are satisfied, but flexibility for different applications decreases

Engineering Contradiction:

Improvemode-specific requirementsVSAvoidflexibility for different applications

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces dynamic reconfiguration capability through switch elements that can change the circuit topology between driving and receiving modes. This dynamic switching allows the same physical circuit to adapt its characteristics to meet different application requirements, enhancing versatility while maintaining mode-specific performance through controlled configuration.

Inventive Principle:

Principle #15Dynamics

3Area of stationary object

If impedance sharing is implemented, then area is reduced, but circuit complexity increases

Engineering Contradiction:

ImproveIO buffer areaVSAvoidcircuit complexity

Core Design Contradiction:

Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent segments the impedance network into modular resistive elements and switch elements that can be independently controlled. This segmentation allows the same physical components to serve different functions in different modes, reducing area while managing complexity through systematic organization of reusable building blocks.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS7755384B2High speed IO buffer

Publication Date: 2010.07.13 MEDIATEK INC

AI summary

A bi-directional buffer is provided. The buffer includes a driver, a receiver, and a circuitry configured to select a driving mode in response to detecting a first condition and to select a receiving mode in response to detecting a second condition. The driving mode has a first impedance and the receiving mode has a second impedance. The second impedance is partially contributed from the driver.