Bandgap-Referenced ADC Calibration Without External Reference Pins

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Solution Overview

Problem

Analog-to-digital converters (ADCs) face challenges in calibration due to limited external pins, which restrict their ability to receive necessary reference signals for accurate calibration, especially in systems with size and cost constraints.

Innovation Solution

The ADC system generates internal reference signals to enable self-calibration, using bandgap voltage generation circuits to produce stable reference voltages that allow for both absolute and relative calibration without requiring external references.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external reference pins are used for ADC calibration, then calibration accuracy is improved, but device complexity and pin count increase

Engineering Contradiction:

ImproveADC calibration accuracyVSAvoidexternal pin network

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The ADC system performs self-calibration using internally generated reference voltages from bandgap circuits, eliminating the need for external reference pins. The system calibrates itself by comparing internal ADC measurements of these reference voltages against expected values and applying corrections to subsequent conversions.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Existing ADC input pins are used for multiple purposes: normal signal conversion and calibration measurements. The same pins that receive external analog signals are also used to measure internally generated reference voltages during calibration, eliminating the need for dedicated calibration pins.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If external reference signals are used for calibration, then measurement precision is improved, but ease of operation deteriorates due to additional hardware requirements

Engineering Contradiction:

Improvecalibration accuracyVSAvoidhardware configuration

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #25Self-service

3Device complexity

If internal reference signals are used for calibration, then device complexity is reduced, but measurement precision may deteriorate without external verification

Engineering Contradiction:

Improveexternal pin networkVSAvoidcalibration accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Physical external reference connections are replaced with electronically generated internal reference voltages. Bandgap circuits generate stable reference voltages internally, and the ADC measures these electronically without requiring physical external reference sources.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 improves the accuracy and precision of digital output signals by allowing internal calibration, reducing the need for external pins and enhancing the ADC's ability to maintain consistent measurements over time and varying conditions.

Implementation Method 1

using bandgap voltage generation circuits to produce stable reference voltages that allow for both absolute and relative calibration without requiring external references

Methodology Applied

Scientific EffectBandgap voltage generation:

Data Source

PatentUS12261617B2Internally calibrated analog-to-digital converter

Publication Date: 2025.03.25 ANALOG DEVICES INT UNLTD CO

AI summary

An analog-to-digital converter (ADC) system for providing a calibrated voltage measurement without an external reference voltage may include an ADC circuit, including an analog ADC input and a digital ADC output. The ADC system may also include circuitry to generate a first internal reference voltage and a second internal reference voltage. The ADC system may also include circuitry configured to provide a selected output from a number of inputs, wherein the inputs include inputs to receive (1) the first internal reference voltage, (2) the second internal reference voltage, and (3) a user-provided analog signal of interest, wherein the selected output can be connected to the analog ADC input, an external voltage measurement device, or both.