Differential ADC Control Using Opposite-Direction LSB Ramps
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Solution Overview
Problem
Existing differential hybrid analog-to-digital converters face disadvantages in their control methods, leading to inefficiencies and performance degradation.
Innovation Solution
A method for controlling an analog-to-digital converter that involves sampling a voltage on multiple digital-to-analog converters, determining most significant bits through successive approximations, and least significant bits through time-to-digital conversion using alternating voltage ramps with opposite directions, reducing harmonics and improving symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control methods are used in differential hybrid analog-to-digital converters, then the conversion process can be completed, but harmonics and noise increase, degrading the figure of merit
Solution Approach 1:
The patent applies asymmetry by using opposite direction ramps for the two differential paths. Instead of symmetric ramping that generates even-order harmonics, the invention uses one ramping up and the other ramping down, which eliminates even-order harmonics and reduces noise, thereby improving the figure of merit while maintaining conversion accuracy.
2Device complexity
If conventional differential hybrid converter control is used, then conversion functionality is maintained, but the number of capacitive elements increases, complicating the device structure
Solution Approach 1:
The patent merges the functionality of multiple capacitive elements by having the first and second digital-to-analog converters share common capacitive structures. The opposite direction ramping allows the same capacitive elements to serve both differential paths, reducing the total number of capacitors needed while maintaining full conversion functionality through coordinated control.
3Productivity
If standard time-to-digital conversion is applied without opposite direction ramps, then least significant bits can be determined, but conversion speed and efficiency are reduced
Solution Approach 1:
The patent implements dynamic opposite direction ramping where the ramp directions are adaptively controlled based on the most significant bit results. This dynamic approach allows the conversion process to proceed faster by eliminating the need for multiple sequential conversions, while the coordinated ramping ensures accurate determination of least significant bits through the differential comparison mechanism.
Data Source
AI summary
The present description provides for a method of controlling an analog-to-digital converter. In an example method, the most significant bits are determined by successive approximations. Further, least significant bits are determined by a time-to-digital conversion by applying a first ramp to the output of a first digital-to-analog converter with a third digital-to-analog converter and by applying a second ramp to the output of the second digital-to-analog converter with a fourth digital-to-analog converter. The variation direction of the first and second ramps is determined by the comparison of the outputs of the first digital-to-analog converter and second digital-to-analog converter at the end of the successive approximations.