SAR ADC Code Shaping for Low-Frequency Error Reduction
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Solution Overview
Problem
Existing A/D conversion circuits face issues with nonlinearity in D/A conversion, leading to errors in A/D conversion data due to periodicity in code data generated by linear feedback shift registers, which affects the Allan dispersion characteristic.
Innovation Solution
A circuit device with a code data generation circuit that generates error data with a shaping frequency characteristic, converting it into code data for A/D conversion, thereby reducing the influence of code shift on the Allan dispersion characteristic by using an inverse function based on the D/A conversion characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If code data is generated by linear feedback shift register to perform code shift, then DNL and INL are improved, but periodicity occurs in code data causing noise components at characteristic frequency that degrade Allan dispersion characteristic
Solution Approach 1:
The invention converts the harmful periodic error components into beneficial shaped noise components by passing the error data through a shaping filter. The filter transforms the spectral characteristics of the periodic errors, spreading them across a broader frequency range and reducing their concentration at characteristic frequencies, thereby improving Allan dispersion while maintaining the code shift functionality for DNL and INL improvement.
Solution Approach 2:
The invention changes the frequency domain parameters of the error data by applying a shaping filter with specific transfer function characteristics. This parameter transformation modifies the spectral density distribution of the periodic errors, converting concentrated periodic components into distributed shaped noise with reduced impact on Allan dispersion measurements.
2Ease of operation
If code shift is performed using code data with periodicity, then A/D conversion is enabled, but error components with characteristic frequency are introduced affecting measurement accuracy
Solution Approach 1:
The shaping filter acts as an intermediary between the periodic code data and the A/D conversion process. It processes the error components generated during code shift, transforming their frequency characteristics before they are combined with the A/D conversion data, thereby reducing the impact of periodic noise on measurement accuracy.
3Reliability
If error data is generated and converted to code data through inverse function, then shaping characteristic is achieved in error frequency, but additional circuit complexity is introduced
Solution Approach 1:
The invention replaces complex mechanical or logical error correction mechanisms with an electronic shaping filter circuit. The filter implements the error transformation function through passive or active electronic components, achieving the desired frequency shaping with simpler and more integrated circuitry compared to alternative error correction approaches.
Data Source
AI summary
A circuit device includes a code data generation circuit that generates code data which changes with time, and a successive approximation type A/D conversion circuit that performs code shift based on the code data and performs A/D conversion of an input signal. The code data generation circuit generates error data of which a frequency characteristic has a shaping characteristic and converts the error data into the code data.