Physical Quantity Detection Circuit Timing for Stable A/D Precharge
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Solution Overview
Problem
Existing physical quantity detection circuits face accuracy degradation due to power supply voltage fluctuations during the precharge period, which affects the A/D conversion process, especially when the start and end timings of the DSP section overlap with the precharge period.
Innovation Solution
The physical quantity detection circuit includes a precharge circuit that precharges the input capacitance of the analog/digital conversion circuit, with the arithmetic processing start and end timings of the digital arithmetic circuit set to avoid the precharge period, ensuring stable power supply and accurate conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the precharge circuit operates during the normal operation period of the digital arithmetic circuit, then the A/D conversion accuracy is improved, but the power supply voltage fluctuates causing output code fluctuation and accuracy degradation
Solution Approach 1:
The operation period of the digital arithmetic circuit is divided into two distinct phases: a normal operation period for arithmetic processing and a conversion period for A/D conversion. This segmentation prevents overlap between precharge operations and arithmetic processing, eliminating power supply voltage fluctuations during precharge while maintaining A/D conversion accuracy.
Solution Approach 2:
The A/D conversion is performed in advance during the conversion period before the normal operation period begins. By completing the conversion beforehand, the input capacitance is fully charged with the correct signal level before any precharge operations occur, ensuring that subsequent precharge activities do not affect the already-converted output code.
2Ease of operation
If the precharge period overlaps with the start or end timing of the DSP section, then the precharge function is maintained, but power supply voltage fluctuation causes precharge output fluctuation and A/D conversion accuracy degradation
Solution Approach 1:
The operation timeline is segmented into distinct conversion period and normal operation period phases. The precharge function operates exclusively during the normal operation period, while A/D conversion occurs during the conversion period. This temporal segmentation ensures that precharge operations never overlap with conversion activities, preventing power supply voltage fluctuations from affecting conversion accuracy.
Solution Approach 2:
The system operates in periodic cycles alternating between conversion period and normal operation period. During each cycle, the precharge circuit activates only during the normal operation period when the digital arithmetic circuit is stable, while A/D conversion occurs during the conversion period. This periodic scheduling prevents harmful overlaps while maintaining both precharge functionality and conversion accuracy.
Data Source
AI summary
A physical quantity detection circuit includes an analog/digital conversion circuit having an input capacitance and sampling an analog signal in the input capacitance to convert the analog signal into a digital signal, a precharge circuit for precharging the input capacitance before the analog/digital conversion circuit sample the analog signal in the input capacitance, a digital arithmetic circuit for performing arithmetic processing to the digital signal, and a reference voltage circuit for supplying a power supply voltage to the precharge circuit and the digital arithmetic circuit, wherein the arithmetic processing start timing and the arithmetic processing end timing of the digital arithmetic circuit are set to the timings avoiding the precharge period in which the precharge circuit precharges the input capacitance.