Sensor Interface Circuit with Redundant Signal Paths for Functional Safety
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Solution Overview
Problem
Current sensor interfaces for automotive applications face challenges in achieving functional safety while minimizing cost and silicon area, as they often rely on multiple sensors to diagnose health and prevent common mode failures, which can be costly and inefficient.
Innovation Solution
A sensor interface circuit that processes a sensor signal into a digital format, storing characterization data for further processing outside the circuit, allowing for comparison of results from different processing means to verify reliability, and optionally using separate conversion paths and additional sensors for enhanced redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple sensors are used to diagnose sensor health and prevent common mode failures, then functional safety is improved, but cost and device complexity increase
Solution Approach 1:
The patent segments the signal processing function across two independent signal paths within a single sensor interface circuit. One path processes the sensor signal through a first conversion chain, while the other path processes the same physical sensor signal through a second conversion chain with different processing steps. This segmentation allows functional safety through comparison without requiring multiple physical sensors, thereby improving reliability while controlling device complexity.
Solution Approach 2:
The sensor interface circuit is designed to perform multiple functions: it can process sensor signals through two different conversion chains, store sensor characterization data, and output both processed results and raw data for external verification. This multi-functionality allows a single circuit to provide both primary measurement and safety verification capabilities, reducing the need for additional separate components.
2Reliability
If multiple sensors are used to diagnose sensor health, then functional safety is improved, but silicon area and cost increase
Solution Approach 1:
The patent merges multiple signal processing functions into a single sensor interface circuit. Both conversion chains share common components such as the sensor element connection, power supply, and portions of the signal conditioning circuitry. The circuit integrates sensor characterization data storage and two independent processing paths within one silicon die, significantly reducing the total silicon area compared to using separate sensors and processing circuits.
Solution Approach 2:
The patent implements a nested structure where sensor characterization data is stored within the sensor interface circuit memory, which is itself integrated with the conversion chains. The first and second conversion chains are nested within the same circuit boundary, sharing common infrastructure. This nesting minimizes the overall silicon footprint by organizing components hierarchically within a single integrated circuit.
3Measurement precision
If sensor signals are processed with compensation and verification, then measurement precision is improved, but processing time and complexity increase
Solution Approach 1:
The patent applies preliminary action by pre-storing sensor characterization data (such as calibration coefficients, temperature compensation data, and sensitivity factors) in the circuit's memory before actual measurement occurs. When a sensor signal is received, the circuit immediately retrieves and applies the appropriate characterization data without waiting for external processing, thereby improving measurement precision while minimizing additional processing time.
Data Source
AI summary
A sensor interface circuit comprises an input arranged to receive a sensor signal being an electrical signal representative of an electrical quantity. The electrical quantity includes a physical quantity converted in a sensor. The sensor interface circuit includes conversion means arranged for converting the sensor signal into a digital signal, memory to store sensor characterisation data, signal processing means adapted to obtain a first sensor result by processing the digital signal using the sensor characterisation data, and an output unit arranged to receive and output the first sensor result, the digital signal and the sensor characterisation data.