Parallel Sample-and-Hold ADC for Continuous Sensor Conversion
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Solution Overview
Problem
In in-vehicle systems, the periodic conversion of analog reference voltage for self-diagnosis interrupts the A/D conversion of analog signals from external sensors, potentially reducing the accuracy of motor drive control and limiting the timing of self-diagnosis, which is not preferable for functional safety.
Innovation Solution
An AD converter with a plurality of analog input terminals, a reference signal generating circuit, a sample-and-hold unit with multiple sample-and-hold circuits, and a control unit that allows parallel operation of sampling and holding analog input signals and reference signals, enabling simultaneous A/D conversion without interrupting the conversion of analog input signals from external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the A/D conversion operation of the analog reference voltage is performed periodically for self-diagnosis, then the functional safety is improved, but the A/D conversion operation of the analog signal from the external sensor is interrupted, reducing the accuracy of the drive control
Solution Approach 1:
The sample-and-hold unit is divided into a first sample-and-hold circuit and a second sample-and-hold circuit. The first circuit handles analog input signals while the second circuit handles the analog reference voltage for self-diagnosis, allowing simultaneous operation without mutual interference.
Solution Approach 2:
The patent combines the self-diagnosis function and the normal A/D conversion function into a single integrated AD converter structure, where both operations can coexist through the use of multiple sample-and-hold circuits working in parallel.
2Measurement precision
If the timing of self-diagnosis using the analog reference voltage is limited to avoid interrupting A/D conversion, then the accuracy of drive control is maintained, but the execution timing of self-diagnosis is restricted, which is not preferable for functional safety
Solution Approach 1:
By segmenting the sample-and-hold functionality into separate circuits, the system enables unrestricted periodic self-diagnosis operations without needing to limit timing, as the diagnostic operations occur in a dedicated circuit that does not interfere with normal conversion operations.
3Device complexity
If a single sample-and-hold circuit is used for A/D conversion, then the device complexity is reduced, but the A/D conversion operation cannot be performed in parallel, reducing productivity
Solution Approach 1:
The sample-and-hold unit is segmented into multiple independent circuits, each capable of operating autonomously. This segmentation enables parallel processing of different analog signals, significantly improving conversion throughput while maintaining reasonable structural complexity.
Solution Approach 2:
Each sample-and-hold circuit is designed with universal functionality to handle both normal analog input signals and the analog reference voltage for self-diagnosis, allowing flexible allocation of resources based on operational requirements.
Data Source
AI summary
An AD converter includes a plurality of analog input terminals, a reference signal generation circuit that generates an analog reference signal, a sample-and-hold unit that includes a plurality of sample-and-hold circuits sampling the analog reference signal or one of analog input signals from the analog input terminals, a control unit that controls the sample-and-hold unit, and a conversion unit that converts an output signal from the sample-and-hold unit into a digital signal. The control unit controls the sample-and-hold unit to perform the output operation for analog input signal and the sampling operation for the analog reference signal.