ICMFB Voltage Monitoring for MEMS Sensor Fault Detection

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Solution Overview

Problem

MEMS sensors, particularly accelerometers, face challenges in differentiating between functional disconnects and reasonable system conditions due to saturation of the analog-to-digital converter, leading to incorrect classification of fault conditions.

Innovation Solution

Monitoring the input common-mode feedback (ICMFB) voltage generated by an ICMFB circuit coupled to the MEMS sensor through multiple nodes, determining the functional state by comparing the output voltage to a threshold, and using this method to distinguish between connected and disconnected states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the ASIC monitors capacitance changes to determine acceleration, then the system can detect acceleration values, but the ADC saturates when nodes are disconnected, making it impossible to differentiate between functional disconnects and extreme acceleration conditions

Engineering Contradiction:
Improveacceleration measurement accuracyVSAvoidfault detection accuracy
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent introduces an intermediary ICMFB voltage signal as a mediator between the MEMS sensor nodes and the ASIC. This ICMFB voltage serves as an additional diagnostic parameter that indicates the electrical connection status of the sensor nodes, allowing the system to distinguish between true acceleration conditions and node disconnects without relying solely on ADC saturation detection

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a feedback mechanism by monitoring the ICMFB voltage output, which reflects the state of the MEMS sensor nodes. This feedback signal is continuously monitored by the ASIC to determine whether the sensor nodes are properly connected, enabling real-time fault detection and differentiation from normal operational conditions

Inventive Principle:
Principle #23Feedback

Data Source

PatentUS12092653B2Sensing an ICMFB output to detect functional state of a mems sensor
Publication Date: 2024.09.17 STMICROELECTRONICS INT NV
  • US12092653B2 patent drawing
  • US12092653B2 patent drawing
  • US12092653B2 patent drawing

AI summary

In one embodiment, a method for detecting functional state of a microelectromechanical (MEMS) sensor is described. The method includes monitoring an input common-mode feedback (ICMFB) voltage generated by an ICMFB circuit coupled to the MEMS sensor through a plurality of nodes. The method also includes determining, using the monitored ICMFB voltage, whether all of the plurality of nodes of the MEMS sensor are electrically connected to the ICMFB circuit.