SAR ADC Correction Circuit for Dielectric Absorption
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Solution Overview
Problem
Dielectric absorption in capacitors of successive approximation register analog to digital converters (SAR ADCs) leads to cross-talk and increased latency, affecting signal-to-noise and distortion ratio (SINAD) and introducing distortion due to the inherent properties of dielectric materials, which worsen with smaller geometries.
Innovation Solution
A correction circuit that adjusts the present digital code value based on a previous digital code value, acquisition time, and temperature, and shuffling capacitors between sampling and bit test stages in PDAC and NDAC to reduce dielectric absorption effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If dielectric absorption is reduced by using materials such as polypropylene, polystyrene, or TEFLON, then dielectric absorption is minimized, but manufacturing complexity and cost increase due to material selection constraints
Solution Approach 1:
The patent converts the harmful dielectric absorption effect into a correctable parameter by measuring the actual absorption in the ceramic capacitor and applying a digital correction factor to the ADC output, thereby eliminating the need to change capacitor materials while achieving the same benefit
Solution Approach 2:
The patent changes the approach from modifying physical material parameters to adjusting digital output parameters, using a correction circuit to modify the digital code based on measured dielectric absorption characteristics, thus avoiding material selection constraints
2Productivity
If capacitor geometry is reduced to increase integration density, then productivity and integration are improved, but dielectric absorption effects worsen
Solution Approach 1:
The patent implements a feedback mechanism where the dielectric absorption correction circuit continuously monitors and compensates for absorption effects in real-time, allowing small capacitors to maintain accurate performance despite inherent absorption issues that would otherwise worsen with reduced geometry
Solution Approach 2:
The patent replaces physical/mechanical solutions (larger capacitor geometries, different materials) with a digital correction system that uses software/algorithms to compensate for physical limitations, enabling continued miniaturization without sacrificing performance
3Device complexity
If dielectric absorption is allowed to affect the conversion, then device complexity is reduced, but measurement precision deteriorates due to cross-talk and distortion
Solution Approach 1:
The patent performs preliminary measurement of dielectric absorption characteristics during capacitor characterization, storing correction factors in advance that are then applied during normal operation, thereby enabling precise compensation without adding complex real-time calculation circuits
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively minimizes dielectric absorption impacts, improving SINAD and reducing latency by accounting for temporal and thermal variations, thereby enhancing the accuracy and reliability of digital conversions.
Implementation Method 1
Dielectric absorption is an intrinsic property of a capacitor to partially recharge itself shortly after it has been discharged. The dielectric absorption phenomenon is a result of dipole or electrical relaxations in the dielectric material disposed between opposed capacitor pates.
Data Source
AI summary
A successive approximation register analog to digital converter (SAR ADC) is provided in which impact of dielectric absorption is reduced with a correction circuit configured to adjust a present digital code value signal based at least in part upon a previous digital code value signal, an acquisition time and temperature.