MOS Voltage Selection Circuit for Low-Drop Terminal Protection

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Solution Overview

Problem

Semiconductor integrated circuit devices face issues with excessive current flow due to incorrect connections among power supply and signal terminals, leading to voltage drops and instability, especially with the use of diode-based protection circuits which incur voltage drops and heat generation as power supply voltages decrease with processing size reduction.

Innovation Solution

A voltage selection circuit utilizing P-type and N-type MOS transistors to select the highest or lowest voltage among multiple input voltages, preventing current flow through parasitic diodes by controlling transistor states and using resistors or diodes to manage voltage drops, ensuring stable operation and reduced power loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If diode-based protection circuits are used to prevent reverse connection, then protection against incorrect connection is achieved, but voltage drop occurs and heat is generated

Engineering Contradiction:

Improveprotection against incorrect connectionVSAvoidvoltage drop and heat generation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the type of component used for protection from diodes to MOS transistors. MOS transistors have much lower on-resistance compared to diodes, resulting in significantly reduced voltage drop and power loss while maintaining the protection function against reverse connection and incorrect terminal connections.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the diode-based protection mechanism with a MOS transistor-based protection mechanism. The MOS transistors are controlled to act as switches that can block reverse current while allowing forward current with minimal voltage drop, substituting the less efficient diode mechanism with a more efficient transistor-based system.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Volume of moving object

If power supply voltage is reduced with processing size reduction, then integration density is improved, but circuit operation stability deteriorates due to voltage drop

Engineering Contradiction:

Improveprocessing sizeVSAvoidcircuit operation stability

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The patent changes from using diodes to using MOS transistors for voltage selection and protection. This parameter change reduces the voltage drop significantly, ensuring that even with reduced power supply voltages from scaling, the circuit receives sufficient voltage for stable operation while maintaining the benefits of smaller processing sizes.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If MOS transistors are used instead of diodes for voltage selection, then voltage drop is suppressed, but device complexity increases

Engineering Contradiction:

Improvevoltage dropVSAvoidcircuit structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The MOS transistors in the patent serve multiple functions: they act as voltage selection switches to suppress voltage drop, provide protection against reverse connection, and enable correct terminal identification. By making the MOS transistors multi-functional, the patent reduces the need for separate protection circuits, thereby limiting the increase in overall device complexity despite the benefits of reduced voltage drop.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9374074B2Voltage selection circuit and semiconductor integrated circuit device having the same

Publication Date: 2016.06.21 ALPS ALPINE CO LTD

AI summary

The highest voltage of a power supply voltage, a ground potential, and a signal voltage is output as a selection voltage from a terminal on the output side. In this case, terminals on the input side and the terminal on the output side are connected to each other through MOS transistors in the ON state. Therefore, it is possible to suppress a voltage drop due to a parasitic diode of each MOS transistor.