FIR Input DAC with Parallel Taps for Pop and Click Reduction
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Solution Overview
Problem
Existing digital-to-analog converters for personal audio devices, such as wireless telephones and media players, face challenges in converting digital PWM signals to analog signals without filtering, which limits their ability to support multi-level signals and results in signal artifacts like 'pops' and 'clicks'.
Innovation Solution
A digital-to-analog converter with an integrator and an input network of parallel taps, each with different signal delays, where control circuitry selectively enables and disables taps to program the effective input resistance and control analog gain, enabling an even number of taps in groups to achieve desired filtering and gain settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a traditional PWM signal conversion approach with serial resistors is used, then the circuit structure is simple, but filtering of the digital input signal cannot occur and signal artifacts like pops and clicks appear
Solution Approach 1:
The patent divides the single conversion path into multiple parallel conversion paths (taps), where each tap processes the PWM signal independently with different resistor values. This segmentation allows the system to implement filtering functionality while maintaining a modular circuit structure that can be systematically expanded.
Solution Approach 2:
The patent combines multiple parallel tap outputs into a single integrated output through summing circuitry. By merging the filtered signals from different taps with varying resistance values, the system achieves comprehensive signal filtering and artifact reduction while preserving the benefits of individual simple tap structures.
2Adaptability or versatility
If no filtering is applied to the digital PWM signal, then the circuit complexity is low, but the converter cannot support multi-level signals and produces distortion
Solution Approach 1:
The patent implements dynamic selectability among multiple parallel taps, where each tap can be independently enabled or disabled based on the desired signal processing requirements. This dynamic configuration allows the system to adapt between different filtering levels and support multi-level signals while maintaining circuit simplicity when full filtering capability is not required.
3Measurement precision
If parallel taps with different resistance values are used, then analog gain control precision is improved, but the device complexity increases
Solution Approach 1:
The patent assigns different resistance values to different parallel taps, creating local quality variations that enable precise analog gain control. Each tap is optimized with specific resistor values tailored to its position in the parallel structure, allowing fine-grained gain adjustment while keeping the overall input network relatively simple through systematic resistor value assignment.
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 reduces signal artifacts and allows for precise control of analog gain, implementing a hybrid analog/digital FIR filter that minimizes distortion and harmonics, while supporting multi-level signals and improving waveform matching.
Implementation Method 1
an integrator, an input network comprising a plurality of parallel taps
Implementation Method 2
each member of the plurality of parallel taps having a signal delay such that at least two of the signal delays of the members of the plurality of parallel taps are different
Data Source
AI summary
A digital-to-analog converter may include an integrator, an input network comprising a plurality of parallel taps, each member of the plurality of parallel taps comprising a respective input resistance, and control circuitry configured to selectively enable and selectively disable particular members of the plurality of parallel taps in order to program an effective input resistance of the input network to control an analog gain of the digital-to-analog converter.