Dynamic Voltage Reference for Delta-Sigma ADC Temperature Drift

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Solution Overview

Problem

Delta-sigma analog-to-digital converters (ADCs) face challenges in maintaining stable reference voltage across varying temperatures due to capacitor mismatch and temperature drift, leading to inaccurate output as the voltage reference circuit's temperature deviates from its calibration point.

Innovation Solution

A dynamic voltage reference circuit with dynamically trimmable capacitors and operational amplifiers that sample diode voltages, allowing for temperature trim calibration and digital gain calibration to maintain stability across a range of temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a voltage reference circuit is calibrated at a single temperature point, then calibration simplicity is improved, but temperature drift increases causing inaccurate output at different temperatures

Engineering Contradiction:

Improvecalibration simplicityVSAvoidoutput accuracy across temperature

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent changes the capacitance parameter of the trimmable capacitor to compensate for temperature drift. By dynamically adjusting the capacitance value based on temperature conditions, the circuit maintains accurate output across varying temperatures without requiring separate calibration at multiple temperature points.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a dynamically trimmable capacitor that can adjust its capacitance value in response to temperature changes. This dynamic adjustment capability allows the voltage reference circuit to adapt to different temperature conditions, maintaining reliability without complex multi-point calibration procedures.

Inventive Principle:

Principle #15Dynamics

2Reliability

If dynamically trimmable capacitors are added to the voltage reference circuit, then temperature drift is reduced, but device complexity increases

Engineering Contradiction:

Improvetemperature stabilityVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the capacitance function into a fixed capacitor and a dynamically trimmable capacitor. This segmentation allows the trimmable portion to be adjusted for temperature compensation while the fixed portion maintains the basic circuit structure, achieving temperature stability with minimal added complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dynamically trimmable capacitor serves multiple functions: it provides temperature drift compensation and enables calibration adjustments. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while achieving improved temperature stability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 across a wide temperature range, minimizing temperature drift and ensuring accurate output even when calibrated at a single temperature point, thus enhancing the reliability of delta-sigma ADCs in cost-sensitive applications.

Implementation Method 1

The voltage reference includes an input capacitor configured to sample an input voltage. The voltage reference includes a base-emitter capacitor configured to sample the first diode voltage with respect to a ground.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

dynamic diode elements configured to provide first and second diode voltages

Methodology Applied

Scientific EffectDiode voltage: Diode

Implementation Method 3

Methodology Applied

Scientific EffectTemperature drift compensation:

Data Source

PatentUS10958285B2Dynamic voltage reference for delta-sigma analog-to-digital converter (ADC) with temperature trim calibration

Publication Date: 2021.03.23 TEXAS INSTRUMENTS INC

AI summary

A calibratable switched-capacitor voltage reference and an associated calibration method are described. The voltage reference includes dynamic diode elements providing diode voltages, input capacitor(s) for sampling input voltages, base-emitter capacitor(s) for sampling one diode voltage with respect to a ground, dynamically trimmable capacitor(s) for sampling the one diode voltage with respect to another diode voltage, and an operational amplifier coupled to the capacitors for providing reference voltage(s) based on the sampled input and diode voltages and on trims of the trimmable capacitor(s). The voltage reference can be configured as a first integrator of a modulator stage of a delta-sigma analog-to-digital converter.