Time Multiplexer Channel Exclusion for A/D Charge Injection Errors
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Solution Overview
Problem
Time multiplexers with open channels cause parasitic charge injection, leading to out-of-range values and errors in A/D conversion due to charging of capacitors, which existing solutions attempt to mitigate by forcing ground inputs or unique software, resulting in performance degradation and increased costs.
Innovation Solution
A method and system that includes a detection logic module to monitor A/D converter outputs for out-of-range values, identifying open channels and excluding further multiplexing from those channels, thereby preventing charge injection errors by modifying the state machine's actions and using a processor with memory to implement corrective actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the time multiplexer continues to multiplex signals from all channels including open channels, then the productivity of the A/D converter is maintained, but charge injection errors occur causing out-of-range values and measurement precision degradation
Solution Approach 1:
The system performs preliminary detection of out-of-range values before they cause charge injection errors to propagate. By monitoring the output of the A/D converter and detecting out-of-range values that indicate open channels, the system takes preventive action by excluding the defective channel from further multiplexing operations, thereby maintaining measurement precision without significantly impacting overall productivity
Solution Approach 2:
The system implements a feedback mechanism where the output of the A/D converter is continuously monitored by a processor. When an out-of-range value is detected, the processor provides feedback to modify the state machine's behavior, causing it to exclude the defective channel from future multiplexing. This closed-loop feedback ensures measurement precision is maintained while minimizing impact on productivity
2Measurement precision
If ground inputs are forced or unique software is used to mitigate open channel effects, then measurement precision is improved, but device complexity and ease of operation worsen
Solution Approach 1:
The system uses the existing A/D converter output as a self-diagnostic tool to detect open channels. By monitoring out-of-range values that naturally occur when channels are open, the system identifies defective channels without requiring external diagnostic equipment or complex additional circuitry. The existing state machine and multiplexer infrastructure are leveraged to implement the exclusion logic, minimizing added complexity
Solution Approach 2:
The processor performing the out-of-range detection serves multiple functions: it monitors A/D converter output for accuracy validation, identifies open channels through pattern recognition, and controls the state machine to exclude defective channels. This multi-functional approach eliminates the need for separate dedicated diagnostic hardware or complex software routines, thereby improving ease of operation while maintaining measurement precision
3Measurement precision
If ground inputs are forced or unique software is implemented to eliminate charge injection, then measurement precision is improved, but ease of operation and productivity deteriorate
Solution Approach 1:
The system automatically detects open channels by monitoring out-of-range values in the A/D converter output and self-corrects by excluding the defective channel from further multiplexing operations. This automatic self-diagnosis and self-correction eliminates the need for manual intervention or complex software configuration, thereby maintaining ease of operation while ensuring measurement precision
Solution Approach 2:
The continuous monitoring of A/D converter output provides real-time feedback about channel status. When an out-of-range value indicates an open channel, the feedback loop automatically triggers exclusion of that channel from future multiplexing operations. This automated feedback mechanism maintains measurement precision without requiring user intervention or complicating system operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively eliminates charge injection errors by preventing further multiplexing from defective channels, ensuring accurate A/D conversion without performance degradation or increased costs, by identifying and managing open channels within the time multiplexer system.
Implementation Method 1
The parasitic output capacitance 26 (CCharge) is charged by the input signal 20a, 20b, 20c or 20d when the corresponding switch 24a, 24b, 24c or 24d is open
Data Source
AI summary
A method and system for monitoring an output of an electronic processing component which detects an out-of-range value in the output of the electronic processing component during one time period during which one channel of input channels of a time multiplexer provides an input signal to the electronic processing component. Corrective actions are performed based on the detected out-of-range value. The corrective actions including excluding further multiplexing of signals from the one channel of the input channels.