ΔΣ ADC Dithering Circuit With Accurate Minute Capacitance
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Solution Overview
Problem
The challenge lies in designing a dithering circuit for ΔΣ analog-to-digital converters that can achieve a small capacitance value with high accuracy, as the required capacitance for generating a minute dither voltage is sensitive to manufacturing variations and local fluctuations, making it difficult to realize in high-withstand voltage applications like automotive systems.
Innovation Solution
The implementation of a dithering circuit with a variable capacitance circuit comprising multiple capacitors connected in series, allowing the control circuit to adjust the capacitance to a value smaller than the maximum capacitance of the capacitors, thereby reducing the impact of manufacturing variations and achieving precise capacitance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sampling capacitance is reduced to increase speed and reduce power, then the dither capacitance also becomes smaller, but it becomes difficult to realize high accuracy capacitance
Solution Approach 1:
The dithering circuit divides the capacitance function into multiple discrete capacitor elements (first capacitor, second capacitor, third capacitor, fourth capacitor) that can be independently controlled. By segmenting the capacitance into switchable units, the circuit achieves precise effective capacitance values even when the total physical capacitance is small, resolving the contradiction between small capacitance size and manufacturing accuracy.
Solution Approach 2:
The dithering circuit dynamically adjusts the effective capacitance by controlling switches to connect or disconnect capacitor elements based on the dither signal requirements. This dynamic switching allows the circuit to maintain accurate capacitance values adaptively, overcoming the static manufacturing variation limitations of small fixed capacitors.
2Use of energy by stationary object
If a small capacitance value is used for dither voltage generation, then power consumption is reduced, but the accuracy is compromised due to manufacturing variations
Solution Approach 1:
The capacitance is segmented into multiple switchable capacitor elements, allowing the circuit to use only the necessary portion for dither voltage generation. This segmentation enables precise control of the effective capacitance value, maintaining accuracy while minimizing the actual capacitance in use, thereby reducing power consumption.
Solution Approach 2:
The circuit changes the effective capacitance parameter dynamically through switch control, adjusting the capacitance value according to the specific dithering requirements. This parameter change capability allows optimization between power consumption and accuracy by selecting appropriate capacitance values for different operating conditions.
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 enables the realization of minute capacitance values with high accuracy, reducing noise influence and eliminating the need for trimming processes, thus lowering costs and improving the reliability of dither voltage generation.
Implementation Method 1
a capacitor circuit including a plurality of capacitors, and a control circuit for causing the capacitor circuit to generate a summed voltage while controlling a capacitance of the capacitor circuit to a capacitance smaller than a capacitance of a capacitor having a maximum capacitance among the plurality of capacitors
Data Source
AI summary
The analog-to-digital converter includes a quantizer for outputting a quantized signal, a sampling circuit for sampling an analog input signal, a dithering circuit for generating an added voltage, and an integrating circuit for integrating a signal on which the added voltage is superimposed and outputting an integration result to the quantizer. The dithering circuit includes a variable capacitance circuit and a control circuit. The variable capacitance circuit includes a plurality of capacitors. The control circuit controls the capacitance of the variable capacitance circuit to a capacitance smaller than the capacitances of the capacitors, and causes the variable capacitance circuit to generate an added voltage.