Bandgap Reference Circuit Low-Voltage Stability

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Solution Overview

Problem

In power management systems, especially in small node ICs below 28 nm, achieving high accuracy and stability of reference voltage is challenging due to variations from error currents, edge voltages, and transistor mismatches, which limits the performance of integrated circuits.

Innovation Solution

A bandgap reference circuit with a proportional to absolute temperature (PTAT) circuit design that includes multiple bipolar junction transistors in parallel arrangements, controlled current generators, and a feedback mechanism to maintain equal supply currents through transistors, reducing temperature dependency and ideality factor fluctuations, thereby stabilizing the reference voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If low supply voltages are used in small node ICs, then power consumption is reduced and integration is improved, but the ability to control variations in reference voltage deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidreference voltage stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the operating parameters of the bandgap reference circuit by carefully selecting transistor aspect ratios, current densities, and bias conditions to optimize performance at low supply voltages. The circuit operates transistors in specific regions where parameter variations have minimal impact on reference voltage stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs feedback mechanisms through carefully designed current mirrors and biasing circuits that automatically adjust operating points to maintain reference voltage stability despite low supply voltage conditions and process variations.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If conventional bandgap reference circuit techniques are used, then reference voltage is generated, but variations from error currents, edge voltages, and transistor mismatches increase

Engineering Contradiction:

Improvereference voltage accuracyVSAvoidvariations from error currents and mismatches

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent extracts and eliminates harmful error currents and edge voltages from the reference voltage generation path by using improved transistor configurations and biasing schemes that prevent these errors from affecting the output.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent applies local quality improvements by optimizing specific regions of the circuit, such as using transistors with matched geometries in critical current mirror paths, adding local compensation elements, and carefully designing the layout to minimize mismatch effects in specific areas.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If transistor mismatches and error currents are present, then circuit operation is simplified, but reference voltage accuracy deteriorates

Engineering Contradiction:

Improvecircuit implementation simplicityVSAvoidreference voltage accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent segments the bandgap reference circuit into functionally independent blocks with well-defined interfaces, allowing each segment to be optimized for its specific function while maintaining overall accuracy. This modular approach enables independent optimization of mismatch-critical sections.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary compensation for expected mismatches and errors during the circuit design and biasing setup phase, using pre-calculated compensation values and predetermined transistor ratio selections that account for typical process variations before the circuit operates.

Inventive Principle:

Principle #10Preliminary action

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

The solution provides a stable reference voltage independent of temperature variations, maintaining high accuracy and performance even at low supply voltages, by ensuring equal supply currents and minimizing mismatches between transistors, thus enhancing the overall performance of integrated circuits.

Implementation Method 1

A bandgap reference circuit with a proportional to absolute temperature (PTAT) circuit design that includes multiple bipolar junction transistors in parallel arrangements

Methodology Applied

Scientific EffectProportional to absolute temperature (PTAT) effect:

Implementation Method 2

The reference voltage produced by the bandgap reference circuit does not significantly vary at low-voltage levels and has a low temperature dependency

Methodology Applied

Scientific EffectBandgap effect:

Data Source

PatentUS10296032B2Bandgap reference circuit

Publication Date: 2019.05.21 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A bandgap reference circuit includes a first bipolar junction transistor (BJT) in series with a first current generator, the first BJT and the first current generator configured to produce a first proportional to absolute temperature (PTAT) signal. The circuit also includes a second BJT in series with a second current generator, the second BJT and the second current generator configured to produce a second PTAT signal. The bandgap reference circuit maintains a current through at least one of the first BJT or the second BJT within a constant ideality factor region of the at least one of the first BJT or the second BJT.