ADC Diagnostic Circuit Using Analog-Digital Signal Comparison
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing analog-to-digital converters (ADCs) in sensors, particularly in safety-critical applications like automobile control systems, face challenges in diagnosing faults effectively, which can lead to manufacturing defects or latent failures, necessitating redundant circuits or self-test capabilities to ensure functional safety.
Innovation Solution
The proposed solution involves diagnostic circuits and methods that compare ADC input signals in both the analog and digital domains, using digital-to-analog converters (DACs) to generate test signals and recover them for fault determination, allowing for the detection of operational status and generation of fault signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant identical circuits are used in a sensor integrated circuit to meet ASIL standards, then reliability is improved, but device complexity increases
Solution Approach 1:
The ADC performs self-diagnostics by comparing its own output against expected values generated from the same input signal through alternative paths (DAC conversion or alternative ADC). The system monitors itself without requiring external test equipment or additional redundant ADC circuits, achieving reliability verification through self-service mechanisms.
Solution Approach 2:
Instead of using redundant identical ADC circuits, the patent creates a digital copy of the ADC output through DAC conversion back to analog domain, or uses alternative conversion paths to generate expected values for comparison. This copying approach verifies ADC functionality without requiring physical redundant hardware.
2Reliability
If self-test capabilities are implemented in ADCs, then reliability is improved, but device complexity increases
Solution Approach 1:
The diagnostic circuit uses the existing DAC and comparator resources for multiple purposes: normal operation and fault detection. The same DAC that converts digital to analog signals also generates test references for ADC verification. The comparator used for normal signal comparison also performs diagnostic verification, eliminating the need for dedicated test hardware.
Solution Approach 2:
The patent introduces a diagnostic module as an intermediary that coordinates the self-test process. This module controls the switching between normal operation and diagnostic modes, manages the comparison process, and generates fault indicators. The intermediary organizes the existing resources into a cohesive diagnostic system without requiring extensive additional circuitry.
3Reliability
If diagnostic circuits are added to monitor ADC operational status, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges the diagnostic function with the existing signal processing path. The same comparator that processes normal signal comparisons is used for diagnostic verification by comparing ADC output with DAC-generated references. The diagnostic functionality is combined with existing hardware resources rather than being implemented as separate dedicated circuits.
Data Source
AI summary
Apparatus includes an ADC configured to convert an analog signal to a digital signal, a comparator having a first input responsive to the analog signal, a second input responsive to the digital signal, and an output at which a comparison signal is provided, and an output checker configured to process the comparison signal to generate a fault signal indicative of whether a fault has occurred in the ADC. The comparator can be an analog comparator in which case the digital signal is converted to an analog signal for the comparison or a digital comparator in which case an additional ADC is provided to convert the analog signal into a digital signal for the comparison. Embodiments include more than one ADC in which case summation elements are provided to sum the analog signals and the digital signals for the comparison.