Dynamic Element Matching with Rate Conversion for Lower DAC Distortion
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Solution Overview
Problem
Conventional dynamic element matching (DEM) circuits in delta-sigma modulator DACs face a trade-off between oversampling ratio and analog distortion, leading to increased distortion due to high-speed switching of analog segments, which affects the distortion performance (THD performance).
Innovation Solution
Implementing a dynamic element matching method where the processing rate for DEM can be set differently from the input rate, either lower or higher, using a DEM circuit with a sampling rate converter and loop filter to reduce the number of analog/digital switching times, thereby improving distortion performance (THD+N) by averaging the use of analog segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the oversampling ratio is increased, then the quantization noise decreases, but the analog distortion increases due to high-speed switching
Solution Approach 1:
The patent applies dynamic element matching (DEM) where the analog segments are dynamically selected and switched based on digital control signals. The switching pattern is dynamically adjusted to distribute the switching activity across multiple analog segments, reducing the distortion caused by high-speed switching while maintaining the benefits of high oversampling ratio.
Solution Approach 2:
The analog portion is divided into multiple analog segments (weight generators) that can be independently controlled. By segmenting the analog structure and selectively activating different segments based on the DEM algorithm, the patent reduces the switching burden on any single segment, thereby reducing distortion while maintaining high oversampling performance.
2Manufacturing precision
If the number of switching times for analog segments is increased to reduce mismatch influence, then the mismatch between analog segments is reduced, but the distortion of the analog portion increases
Solution Approach 1:
The patent implements dynamic element matching where the selection of analog segments is dynamically controlled based on digital signals. The DEM circuit dynamically adjusts which analog segments are active and when they are switched, optimizing the trade-off between mismatch reduction and distortion minimization. This dynamic control allows the system to reduce mismatch influence without proportionally increasing distortion.
Data Source
AI summary
The invention provides an improved dynamic element matching (DEM) device. The DEM device performs dynamic element matching processing at a second timing rate different from the first timing rate for the digital input. As an embodiment, the DEM device is composed of encoder 10 and feedback circuit 12. Said encoder 10 has two inputs and one output. Of the two inputs, one receives the digital input as the object for the DEM processing, and the other input receives the output of feedback circuit 12. Then, the digital output of the encoded result is generated. Said feedback circuit 12 has sampling rate converter 120 and loop filter 122 in order to perform DEM processing at a timing rate different from the timing rate for the digital input as the DEM processing object.