Sigma-Delta Modulator Reference Split for Lower Power Swing
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Solution Overview
Problem
Conventional sigma-delta modulators experience high power consumption due to large equivalent loading capacitors and high current consumption, especially in high-resolution audio applications where reference voltages create significant potential differences, leading to increased power consumption and current demand.
Innovation Solution
A sigma-delta modulator design that utilizes independent reference voltages for the quantizer and digital-to-analog converter, where the difference between the first positive and negative reference voltages is smaller than that of the second positive and negative reference voltages, reducing the weighting gain and power consumption by configuring the gain amplifiers and capacitors to operate within a reduced voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the adder takes in several signals with large potential difference, then the output swing approaches the potential difference between Vdd and Gnd, but the power consumption of the adder circuit becomes considerably large
Solution Approach 1:
The patent divides the reference voltage system into two independent sets: one for the quantizer and another for the digital-to-analog converter. This segmentation allows each block to operate with optimized reference voltages, preventing the adder from handling the full potential difference and thereby reducing power consumption while maintaining output swing performance.
Solution Approach 2:
Different reference voltage levels are assigned to different functional blocks based on their specific requirements. The quantizer uses reference voltages optimized for its operation, while the digital-to-analog converter uses separate reference voltages. This local optimization ensures that the adder does not need to accommodate the maximum potential difference across the entire system, reducing its power consumption.
2Speed
If high-speed broadband sigma-delta modulator is designed with high slew rate, then the modulation performance is improved, but the current consumption becomes large
Solution Approach 1:
The patent segments the reference voltage supply into independent blocks, allowing the quantizer and digital-to-analog converter to operate with optimized voltage levels. This reduces the overall voltage swing requirements in the signal path, enabling high slew rate operation with lower current consumption since the capacitors and amplifiers do not need to charge/discharge across the full potential difference.
3Reliability
If the equivalent loading capacitor of the adder is much greater than that of the integrator, then the filter functionality is achieved, but the power consumption increases
Solution Approach 1:
The patent applies local optimization by assigning different reference voltage levels to different functional blocks. This allows the filter to maintain its required capacitance ratios and functionality while operating within a reduced voltage range, thereby reducing the power consumption associated with charging and discharging the capacitors.
Data Source
AI summary
A sigma-delta modulator includes a first adder, a filter, a quantizer and a digital-to-analog converter. The first adder receives an input signal and an analog signal and subtracts the analog signal from the input signal to output a processed signal. The filter receives the processed signal to output a filtered signal. The quantizer receives the filtered signal to generate an output signal. The quantizer works based on a first positive reference voltage and a first negative reference voltage. The digital-to-analog converter generates the analog signal according to the output signal and outputs the analog signal to the first adder. The digital-to-analog converter works based on a second positive reference voltage and a second negative reference voltage. A difference between the first positive reference voltage and the first negative reference voltage is smaller than a difference between the second positive reference voltage and the second negative reference voltage.