CMOS Logic Circuit Temperature Compensation Single Current Source

Solution Overview

Problem

Current solutions for temperature compensation in CMOS logic circuits, such as ring oscillators, require multiple current sources to minimize temperature variation effects, leading to increased bulk and consumption.

Innovation Solution

A method using a single current source to generate a supply current that accounts for temperature variations in transistor threshold voltages by forming a second current representative of these variations, limited to a fraction of the first current, to control the propagation time of CMOS logic circuits and oscillator frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple current sources (PTAT and CTAT) are used for temperature compensation, then frequency stability is improved, but device bulk and power consumption increase

Engineering Contradiction:

Improvefrequency stabilityVSAvoiddevice bulk

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the functions of multiple current sources into a single current source that generates a compensation current accounting for both PTAT and CTAT effects. This single current source provides temperature compensation for oscillator frequency while reducing device bulk and power consumption compared to using separate PTAT and CTAT current sources.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single current source is designed to perform multiple functions: it generates a compensation current that accounts for temperature variations in transistor threshold voltages and provides temperature compensation for the oscillator frequency. This multi-functional approach eliminates the need for separate dedicated PTAT and CTAT current sources.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multiple current sources (PTAT and CTAT) are used for temperature compensation, then frequency stability is improved, but power consumption increases

Engineering Contradiction:

Improvefrequency stabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent merges the functions of multiple current sources into a single current source that generates a compensation current accounting for both PTAT and CTAT effects. This single current source provides temperature compensation for oscillator frequency while reducing device bulk and power consumption compared to using separate PTAT and CTAT current sources.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single current source is designed to perform multiple functions: it generates a compensation current that accounts for temperature variations in transistor threshold voltages and provides temperature compensation for the oscillator frequency. This multi-functional approach eliminates the need for separate dedicated PTAT and CTAT current sources.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Stability of the object's composition

If temperature compensation is implemented using conventional methods, then propagation time variation is reduced, but device bulk increases

Engineering Contradiction:

Improvepropagation time stabilityVSAvoiddevice bulk

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent merges the functions of multiple current sources into a single current source that generates a compensation current accounting for both PTAT and CTAT effects. This single current source provides temperature compensation for oscillator frequency while reducing device bulk and power consumption compared to using separate PTAT and CTAT current sources.

Inventive Principle:

Principle #5Merging (Combining)

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 allows for controlled temperature variation of propagation time within a narrow range and reduced bulk and consumption, maintaining frequency stability with minimal sensitivity to temperature changes.

Implementation Method 1

A first current that is proportional to absolute temperature is generated

Methodology Applied

Scientific EffectPTAT (Proportional to Absolute Temperature):

Implementation Method 2

A second current is formed. The second current is representative of the temperature variation of the threshold voltages of the transistors of the inverter and is limited to a fraction of the first current

Methodology Applied

Scientific EffectTemperature variation of threshold voltages:

Data Source

PatentUS9325325B2Method and device for managing the time transition of a CMOS logic circuit as a function of temperature

Publication Date: 2016.04.26 STMICROELECTRONICS INT NV

AI summary

A method includes generation of a first current proportional to absolute temperature and formation of a second current representative of the temperature variation of the threshold voltages of the transistors of the inverter and limited to a fraction of the first current. This fraction is less than one. The inverter is supplied with a supply current equal to the first current minus the limited second current.