MCU Low Power Mode Leakage Reduction via Threshold Voltage Adjustment

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Microcontroller units (MCUs) face significant leakage current issues during low power sleep modes due to sub-threshold conduction in transistors, which increases power consumption despite suspended clock operations, especially as transistor dimensions shrink.

Innovation Solution

A low power system that includes an internal voltage generator to increase the voltage difference between digital circuit portions and the terminals during low power mode, allowing the voltage across digital circuits to be less than the full voltage, thereby reducing leakage current by adjusting the threshold voltage of transistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the clock is suspended during sleep mode to reduce power consumption, then power consumption is reduced, but leakage current through transistors increases due to sub-threshold conduction

Engineering Contradiction:

Improvepower consumptionVSAvoidleakage current

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent adjusts the threshold voltage of transistors during sleep mode by modifying the voltage difference across digital circuit portions. An internal voltage generator increases the voltage difference between digital circuit portions and terminals, effectively changing the electrical parameters to reduce sub-threshold conduction and leakage current while maintaining state information.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If transistor dimensions are reduced to advance technology, then device density and performance improve, but leakage current increases due to enhanced sub-threshold conduction

Engineering Contradiction:

Improvedevice densityVSAvoidleakage current

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent compensates for increased leakage in scaled transistors by dynamically adjusting threshold voltage parameters during sleep mode. The internal voltage generator modifies the voltage distribution across digital circuit portions, effectively changing electrical parameters to counteract the enhanced sub-threshold conduction inherent in smaller transistor dimensions.

Inventive Principle:

Principle #35Parameter changes

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 minimizes leakage current and power consumption during low power modes, allowing MCUs to maintain state information for efficient wake-up and prolong battery life in applications like implanted devices.

Implementation Method 1

there is still the possibility for some 'sub-threshold conduction.' This is the condition that, even though the transistor is operating below its threshold voltage, the transistor can still conduct.

Methodology Applied

Scientific EffectSub-threshold conduction:

Data Source

PatentUS7493505B2MCU with low power mode of operation

Publication Date: 2009.02.17 SILICON LABORATORIES INC

AI summary

A low power system is disclosed for working in conjunction with a digital circuit that is disposed between positive and negative terminals. The system includes an internal voltage generator for increasing, for at least a first portion of the digital circuit, a voltage difference between the at least a first portion of the digital circuit and the voltage on at least one of the positive and negative terminals during a low power mode of operation. This allows the voltage across the at least first portion of the digital circuit to be less than the full voltage across the positive and negative terminals.