Reference Buffer Integrating ADC Capacitor for Noise Reduction

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Solution Overview

Problem

Existing reference buffer technologies face challenges in maintaining accurate reference voltage for analog-to-digital converters (ADCs) due to power consumption variability and increased cost and size from using external capacitors, which are prone to inaccuracies under piezoelectric stresses.

Innovation Solution

A reference buffer topology with an integrator, internal capacitor, and separate gain stages, incorporating a low-pass feedback loop to reduce low-frequency noise and quiescent current, allowing for a single integrated circuit solution with minimal external components, reducing pin count and improving performance in industrial scenarios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If external capacitors are used in reference buffer, then reference voltage accuracy is improved, but cost and circuit size increase

Engineering Contradiction:

Improvereference voltage accuracyVSAvoidcircuit size

Core Design Contradiction:

Measurement precisionVSArea of stationary object

Solution Approach 1:

The patent combines the capacitor function directly into the reference buffer circuit by using the ADC's existing capacitor as the reference buffer capacitor, eliminating the need for separate external capacitors. This integration reduces circuit size and component count while maintaining reference voltage accuracy through the buffer's internal architecture.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The reference buffer is designed to serve multiple functions: it provides reference voltage buffering, filters noise through its internal capacitor, and interfaces with the ADC using the ADC's own capacitor. This multi-functionality eliminates the need for dedicated external capacitors, reducing overall circuit size while maintaining accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If external capacitors are used in reference buffer, then reference voltage accuracy is improved, but cost increases

Engineering Contradiction:

Improvereference voltage accuracyVSAvoidcost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent merges the reference buffer capacitor function with the ADC's internal capacitor, eliminating the need for separate external capacitor components. This reduction in component count directly lowers manufacturing cost while maintaining reference voltage accuracy through the buffer's internal design.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The reference buffer design allows the ADC's own capacitor to serve dual purposes: as the ADC's internal capacitor and as the reference buffer's capacitor. This self-service approach eliminates the need for additional external capacitors, reducing both cost and component count while maintaining performance.

Inventive Principle:

Principle #25Self-service

3Stability of the object's composition

If reference buffer is added to maintain reference voltage accuracy, then reference voltage stability is improved, but device complexity increases

Engineering Contradiction:

Improvereference voltage stabilityVSAvoidcircuit complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent combines the reference buffer functionality with the ADC's existing capacitor and internal architecture, eliminating the need for separate external components. This integration maintains reference voltage stability through the buffer's internal design while reducing overall circuit complexity by removing external components and simplifying the bill of materials.

Inventive Principle:

Principle #5Merging (Combining)

4Measurement precision

If integrator and gain stages are integrated into reference buffer, then reference voltage accuracy is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvereference voltage accuracyVSAvoidcircuit fabrication precision

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent integrates the integrator and gain stages within the reference buffer using the ADC's existing capacitor and internal architecture. By consolidating these functions into a single integrated circuit block, the patent reduces the number of discrete components and interconnections, thereby reducing cumulative manufacturing tolerances and improving overall manufacturing precision despite the enhanced functionality.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10747249B1Reference buffer with integration path, on-chip capacitor, and gain stage separate from the integration path

Publication Date: 2020.08.18 TEXAS INSTRUMENTS INC

AI summary

A system includes: a reference buffer coupled to an input supply voltage; an analog-to-digital converter (ADC) coupled to an output of the reference buffer; and an output capacitor coupled between the output of the reference buffer and a ground node. The reference buffer includes: an integrator; an internal capacitor coupled between an output of the integrator and the ground node; a first gain stage with an input coupled to the output of the reference buffer; and a second gain stage with an input coupled to the output of the integrator. The output of the first gain stage is combined with the output of the integrator using a combine circuit.