Time-Domain ADC Reference Switching for High Dynamic Range
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Solution Overview
Problem
Conventional A/D converters in sensor devices face challenges in achieving high dynamic range at high speed and low power consumption, with existing solutions either compromising on conversion frequency or increasing power consumption.
Innovation Solution
A time domain A/D converter system utilizing two reference voltage signals and a delay locked loop circuit to perform A/D conversion, with a reference voltage selection circuit that switches between full-scale and limited voltage range signals, and a comparator control circuit to optimize conversion speed and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional A/D converters use single reference voltage for full-scale conversion, then conversion speed is maintained, but noise decreases poorly and dynamic range is limited
Solution Approach 1:
The reference voltage generation is segmented into two distinct circuits: a first reference signal generation circuit for full-scale conversion and a second reference signal generation circuit for limited voltage range conversion. This segmentation allows each circuit to be optimized for its specific function, with the second circuit able to perform repeated conversions at the same voltage level to reduce noise through averaging, thereby improving dynamic range without compromising conversion speed
Solution Approach 2:
The system dynamically switches between two reference voltage modes based on the input signal characteristics. The reference voltage selection circuit determines whether to use the first reference signal (full-scale) or the second reference signal (limited range) based on the detected input signal level, enabling adaptive optimization of both conversion speed and noise performance for different signal conditions
2Productivity
If A/D converter increases conversion frequency, then speed is improved, but power consumption increases
Solution Approach 1:
For signals within a limited voltage range, the system performs more conversion operations than the minimum single full-scale conversion would require. By repeatedly converting the same signal multiple times using the second reference signal and averaging the results, the system achieves noise reduction equivalent to what would require much higher conversion frequencies, thereby reducing power consumption while maintaining effective conversion speed
3Measurement precision
If A/D converter uses multiple reference voltages for noise reduction, then dynamic range improves, but device complexity increases
Solution Approach 1:
The system merges two reference signal generation circuits into a unified A/D conversion architecture with a single switching mechanism. The reference voltage selection circuit integrates the choice between first and second reference signals, and the accumulation adder-subtracter combines multiple conversion results into a single averaged output. This merging approach achieves noise reduction through multiple conversions while presenting a relatively simple unified interface, preventing excessive complexity growth
Data Source
AI summary
A time domain A/D converter group includes a plurality of individual A/D converters, each of the individual A/D converters is connected to a reference signal generation circuit to generate a first reference signal for sweeping in a full scale range and a second reference signal for repeating plurality of times to sweep in a limited voltage range, and each of the individual A/D converters includes a reference voltage selection circuit for switching the first reference signal or the second reference signal, a comparator for comparing an input signal with the first reference signal or the second reference signal, for generating a comparison output signal, an internal A/D converter for performing an A/D conversion using the comparison output signal from the comparator, and an accumulation adder-subtractor for outputting an average signal of A/D conversion values obtained from the A/D conversion when the second reference signal is selected.