Sigma-Delta ADC Feedback Switching for Lower Thermal Noise
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Solution Overview
Problem
Existing delta sigma modulators face challenges in maintaining high Signal-to-Noise Ratio (SNR) performance due to increased circuit complexity and area requirements when using feedback digital-analog converter (DAC) technology with filters.
Innovation Solution
The semiconductor device incorporates an integrator, quantizer, and a feedback circuit with switches controlled by digital signals to manage reference voltages applied to resistors, optimizing their connection to input terminals based on control signals generated from digital output signals and their delayed versions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback digital-analog converter (DAC) technology with filters is used to reduce degradation of Signal-to-Noise Ratio (SNR) performance, then SNR performance is improved, but device area and circuit complexity increase
Solution Approach 1:
The patent extracts and removes the filter component from the feedback DAC circuit, keeping only the essential feedback functionality. This eliminates the complexity and area overhead of filters while maintaining the core SNR improvement benefit through selective resistor connection control.
Solution Approach 2:
The patent introduces dynamic control of resistor connections through switches that are selectively turned on and off based on feedback digital signals. This dynamic switching mechanism replaces the static filter structure, providing adaptive feedback control without the complexity of filter circuits.
2Reliability
If feedback digital-analog converter (DAC) technology with filters is used to reduce degradation of Signal-to-Noise Ratio (SNR) performance, then SNR performance is improved, but device area increases
Solution Approach 1:
The patent extracts and removes the filter component from the feedback DAC circuit, keeping only the essential feedback functionality. This eliminates the complexity and area overhead of filters while maintaining the core SNR improvement benefit through selective resistor connection control.
Solution Approach 2:
The patent uses switch elements that can be controlled by digital signals to replicate the filtering function in a much more compact form. The switches copy the essential feedback action without requiring the physical filter structure, significantly reducing area.
3Reliability
If resistors are continuously connected to the integrator, then feedback operation is maintained, but thermal noise increases
Solution Approach 1:
The patent implements periodic switching of the resistor connections to the integrator based on the feedback digital signals. The resistors are connected only during specific periods when feedback is needed, and disconnected during other periods, creating a periodic action pattern that maintains feedback operation while minimizing thermal noise exposure time.
Solution Approach 2:
The patent introduces dynamic control of resistor connections through switches that are selectively turned on and off based on feedback digital signals. This dynamic switching mechanism replaces the static filter structure, providing adaptive feedback control without the complexity of filter 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
This configuration reduces thermal noise and improves operating performance by disconnecting resistors from the integrator during non-feedback operations, thereby minimizing thermal noise and enhancing SNR performance.
Implementation Method 1
a first switch configured to control application of a first reference voltage to a first resistor based on a first control signal, a second switch configured to control application of a second reference voltage to the first resistor based on a second control signal
Implementation Method 2
an integrator configured to receive a first input signal through a first input terminal and output a corresponding first output signal, and to receive a second input signal through a second input terminal and output a corresponding second output signal
Implementation Method 3
a quantizer configured to generate a first digital signal based on the first and second output signals
Implementation Method 4
a third switch configured to control connection between the first resistor and the first input terminal based on a third control signal. The third switch is turned on when any one of the first and second switches is turned on, and the third switch is turned off when both the first and second switches are turned off
Data Source
AI summary
A semiconductor device such as a sigma delta A/D converter includes an integrator configured to output first and second output signals, a quantizer configured to generate a first digital signal based on the output signals, first and second switches configured to control application of first and second reference voltages to a first resistor based on respective first and second control signals, and a third switch configured to control connection between the first resistor and a first input terminal of the integrator based on a third control signal. The first through third control signals are generated based on the first digital signal and a second digital signal obtained by delaying the first digital signal. The third switch is turned on when any one of the first and second switches is turned on, and is turned off when both the first and second switches are turned off.