Variable Period Calibration for Digital Analog Converter Distortion
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Solution Overview
Problem
Monolithic integrated digital/analog converters face mismatches between converter cells, leading to distortions in the output spectrum, which limit the interference-free dynamic range and overall performance, especially as integration increases, and existing calibration methods generate additional interfering frequencies.
Innovation Solution
Implementing a calibration method that uses variable calibration periods for each converter cell, determined by a control device or random number generator, allowing for different calibration periods in each calibration cycle to reduce distortions and improve the interference-free dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant calibration periods are used for all converter cells, then the calibration process is simple and systematic, but additional interfering frequencies are generated at the calibration frequency and its multiples
Solution Approach 1:
The patent applies dynamics by making the calibration periods variable rather than constant. Each converter cell is assigned a different calibration period, and these periods can be changed between calibration loops. This dynamic approach prevents the generation of fixed interfering frequencies at specific harmonics, thereby resolving the contradiction between calibration simplicity and interference generation.
Solution Approach 2:
The patent changes the parameter of calibration period from a fixed constant value to a variable value that differs for each converter cell and can change between calibration loops. This parameter change eliminates the periodic repetition that causes interfering frequencies at specific frequency multiples, while still maintaining a systematic calibration process.
2Manufacturing precision
If calibration is performed for each converter cell, then mismatches are corrected and output spectrum distortions are reduced, but the calibration process becomes time-consuming and complex
Solution Approach 1:
The patent segments the calibration process by assigning different calibration periods to different converter cells. This segmentation allows each cell to be calibrated independently with its own timing characteristics, correcting mismatches effectively while organizing the complexity into a manageable structured approach rather than a monolithic process.
Solution Approach 2:
By introducing dynamic variation in calibration periods across different cells and loops, the patent achieves precise calibration of each converter cell while avoiding the need for overly complex synchronized calibration schemes. The dynamic timing simplifies the overall control logic compared to rigid constant-period calibration of all cells.
3Area of stationary object
If integration is increased to reduce converter size, then chip area is reduced and costs are lowered, but mismatches between converter cells become more predominant
Solution Approach 1:
The patent implements self-service through online calibration that automatically corrects mismatches between converter cells. The calibration process is integrated into the normal operation, allowing the D/A converter to self-correct the precision degradation that occurs with increased integration, thereby maintaining high manufacturing precision despite smaller cell sizes and larger cell counts.
Solution Approach 2:
The patent uses feedback mechanisms where the calibration process continuously monitors and corrects mismatches between converter cells. This feedback loop compensates for the increased variability inherent in highly integrated designs with many small cells, maintaining precision without requiring larger physical cell sizes.
Data Source
AI summary
A digital/analog converter comprises a converter array comprised of a plurality of converter cells and a device for self-calibration of the converter cells. The device for self-calibration comprises at least one reference cell with a reference value and a control device for controlling a calibration process. The control device calibrates successively, within a respective calibration period, respective of the converter cells to values corresponding to the reference value and adjusts respective calibration periods for a calibration cycle, within which the converter cells are to be calibrated. At least two different of the respective calibration periods differ within at least two calibration cycles.