Segmented S/H Capacitor ADC for Automatic Gain Ranging
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Solution Overview
Problem
Existing analog-to-digital converter (ADC) circuits face challenges in achieving high dynamic range and optimal noise performance, as they often require anticipating the necessary input range for accurate conversion, which can be difficult in varying measurement scenarios.
Innovation Solution
The implementation of a high dynamic range ADC circuit that includes a separate sample-and-hold (S/H) capacitor segmented into multiple capacitors, with a second circuit performing coarse quantization to determine the number of capacitors to use based on the input signal, allowing for automatic gain ranging and adjustment of the full-scale input range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed sampling capacitor is used in the ADC circuit, then the circuit structure is simple, but the dynamic range and noise performance cannot be optimized for varying input signal magnitudes
Solution Approach 1:
The sampling capacitor is divided into multiple segments (first sampling capacitor, second sampling capacitor, etc.), each with different capacitance values. A capacitor selection circuit selectively connects appropriate segments based on the input signal magnitude, enabling dynamic range adaptation while maintaining manageable circuit complexity through modular design
Solution Approach 2:
The sampling capacitor configuration is made dynamic through automatic gain ranging. The capacitor selection circuit adjusts which capacitors are connected in parallel based on the magnitude of the input signal, allowing the total sampling capacitance to vary dynamically rather than being fixed, thus optimizing performance for different signal levels
2Measurement precision
If the sampling capacitor size is increased to improve resolution for small signals, then noise performance improves, but the full-scale input range decreases
Solution Approach 1:
By segmenting the sampling capacitor into multiple units with different capacitance values, the system can select and combine specific segments based on signal magnitude. This allows using larger capacitance (for better resolution) when signals are small, and smaller capacitance (for larger input range) when signals are large, resolving the trade-off between resolution and input range
Solution Approach 2:
The sampling capacitance parameter is made variable through automatic gain ranging. The capacitor selection circuit changes the effective capacitance value based on input signal characteristics, allowing the system to optimize the capacitance parameter for each specific signal level, thereby achieving both high resolution for small signals and large input range for big signals
3Measurement precision
If automatic gain ranging is implemented with multiple sampling capacitors, then resolution and noise performance are optimized, but the device complexity increases
Solution Approach 1:
The sampling capacitor is segmented into multiple manageable units that can be selectively connected. This segmentation allows the system to achieve optimized noise performance through dynamic capacitance selection while keeping each individual capacitor unit simple and the overall architecture organized, preventing exponential complexity growth
Solution Approach 2:
A capacitor selection circuit is implemented that performs preliminary assessment of the input signal magnitude and pre-selects the appropriate capacitor configuration before the main conversion process. This preliminary action optimizes the sampling capacitance in advance, ensuring best noise performance without requiring complex real-time adjustments during conversion
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
This approach enhances resolution and noise performance by dynamically adjusting the sampling capacitance, improving the ADC's ability to handle signals across a wide range without pre-estimating the required input range.
Implementation Method 1
a plurality of sampling capacitors configured to: receive the analog input signal; and couple to the first ADC circuit
Data Source
AI summary
Techniques to provide automatic-gain ranging for high dynamic range by including a separate S/H capacitor, segmenting the S/H capacitor into a plurality of capacitors, and determining the number of segments to use for a sample. In this manner, the size of the S/H capacitor can be changed (by adjusting the number of capacitors), which can change the amount of input voltage that produces an amount of charge. Using these techniques, the full-scale input range for a sample of the analog input signal can be adjusted automatically based on the magnitude of the sample, which can provide better resolution and/or better noise performance for that particular sample then would otherwise be possible.