Floating Attenuator Front End for Beyond-the-Rails Voltage Sensing

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Solution Overview

Problem

Traditional continuous-time analog front ends for voltage sensing in ADCs consume static power, making them unsuitable for ultra-low power consumption applications, especially in battery-operated devices.

Innovation Solution

A system comprising a passive floating attenuator, anti-aliasing filter, and switched-capacitor sampling circuit is used to attenuate and filter analog signals, enabling beyond-the-rails voltage sensing with ultra-low power consumption by using a bootstrapped switch circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a continuous-time analog front end is used for voltage sensing, then the sensing function is achieved, but static power consumption increases

Engineering Contradiction:

Improvevoltage sensing capabilityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent employs a switched-capacitor circuit that operates in periodic cycles, using periodic switching actions to perform attenuation and filtering functions. This replaces the continuous operation of traditional analog front ends with periodic discrete operations, significantly reducing power consumption while maintaining sensing functionality.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent substitutes traditional continuous-time analog circuitry with a switched-capacitor system that uses periodic switching and capacitive storage. This mechanical-like switching approach replaces continuous electronic signal processing, enabling ultra-low power operation while achieving the same voltage sensing and filtering objectives.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If a switched-capacitor sampling circuit is used, then power consumption is reduced, but the circuit complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoidcircuit complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The switched-capacitor circuit is designed to perform multiple functions including attenuation, filtering, and sampling within a single integrated structure. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby managing overall circuit complexity while achieving ultra-low power operation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the attenuator and anti-aliasing filter into a single switched-capacitor based front-end circuit. By merging these functions into one unified circuit block rather than using separate discrete circuits, the overall device complexity is managed while still achieving the desired power reduction benefits.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS12618880B2Ultra-low-power front end for beyond-the-rails voltage sensing

Publication Date: 2026.05.05 CIRRUS LOGIC INC

AI summary

A system may include a passive floating attenuator configured to receive an analog physical quantity and attenuate the analog physical quantity to a floating attenuated signal defined by voltage nodes other than the voltage nodes of the analog physical quantity, an anti-aliasing filter configured to filter the floating attenuated signal to generate a filtered attenuated signal, and a switched-capacitor sampling circuit comprising a plurality of switches configured to sample the filtered attenuated signal.