Level Shifter Output Control for Low-Power Fixed Logic States

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Solution Overview

Problem

Conventional level shifters in mobile devices face issues with power consumption when in a high impedance or meta-stable state, leading to unpredictable output signals and excessive current flow, which increases power consumption.

Innovation Solution

A level shifter circuit comprising a level shifting unit, current suppression circuits, and an output control circuit, where the current suppression circuits use MOS transistors to block current flow and the output control circuit connects the output terminal to a power supply or ground voltage in an input suppression mode, ensuring fixed output values and reduced power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If power is cut to the level shifter to reduce power consumption, then power consumption is reduced, but the output signal becomes unstable and excessive current may flow

Engineering Contradiction:

Improvepower consumptionVSAvoidoutput signal stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent introduces a pull-up resistor and pull-down resistor as intermediary components connected to the output terminal. These resistors act as mediators that define a default voltage state (logic high or logic low) when the level shifter is in high-impedance mode, preventing the output from floating and ensuring stable signal levels even when power is cut to the level shifter.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the electrical state parameters of the output terminal by introducing resistive elements that establish defined voltage levels. When the level shifter is powered down, the resistors control the output voltage to remain at a stable logic level rather than floating, thus changing the electrical parameter stability without requiring continuous power supply to the level shifter.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the output terminal is left in high impedance state to save power, then power consumption is reduced, but other function blocks cannot operate normally

Engineering Contradiction:

Improvepower consumptionVSAvoidnormal operation of connected function blocks

Core Design Contradiction:

Use of energy by moving objectVSEase of operation

Solution Approach 1:

The pull-up and pull-down resistors serve as intermediary components that actively manage the output terminal state. When the level shifter is in high-impedance mode, these resistors mediate between the disconnected level shifter and the connected function blocks, ensuring the output terminal presents a valid logic level that allows connected blocks to operate normally.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The resistors are pre-configured to establish a default output state before the level shifter is powered down. This preliminary action ensures that when power is cut, the output terminal already has a defined voltage level, preventing connected function blocks from encountering undefined or floating signals.

Inventive Principle:

Principle #10Preliminary action

3Use of energy by moving object

If the output terminal is in meta-stable state, then power consumption is reduced, but excessive current may abruptly flow in the level shifter

Engineering Contradiction:

Improvepower consumptionVSAvoidexcessive current flow

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The pull-up and pull-down resistors act as protective intermediary elements that limit current flow. When the output terminal might otherwise enter a meta-stable state, these resistors provide defined current paths that prevent excessive current from flowing, thus protecting the level shifter while maintaining low power consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The resistors are configured in advance to cushion against potential harmful effects. By establishing defined voltage levels and current paths before meta-stable conditions can develop, the resistors prevent excessive current flow while allowing the level shifter to remain in a low-power state.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS7881756B2Level shifters and level shifting methods for suppressing current flow and generating fixed output values

Publication Date: 2011.02.01 SAMSUNG ELECTRONICS CO LTD

AI summary

A level shifter includes a level shifting circuit which receives input signal from a function block and changes the voltage level of the input signal, to output an output signal; a current blocking circuit, which suppresses current flowing to the level shifting circuit in an input suppression mode in which power supplied to the function block is cut and deactivates the level shifting circuit; and an output control circuit, which controls the output signal of the level shifting circuit to have a direct current (DC) voltage level in the input suppression mode.