DAC Current Source Calibration via Sorting and Switching Sequences
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Solution Overview
Problem
Conventional digital-to-analog converters (DACs) and echo cancellers face challenges in matching current sources, leading to poor linearity and ineffective echo cancellation due to integral non-linearity differences, resulting in unstable echo compensation and additional noise generation.
Innovation Solution
A method and system for calibrating output currents by performing sorting operations on current sources and determining switching sequences to align their output levels, ensuring matching between different current sources in DACs and echo cancellers, thereby improving linearity and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple current sources are used in DAC to achieve desired output current values, then the output current range is improved, but the linearity between analog output current signal and digital input numerical signal deteriorates due to process differences causing different current levels from same target current value
Solution Approach 1:
The patent applies parameter changes by adjusting the switching sequences of current sources based on their actual measured current levels. Instead of using fixed switching sequences, the system dynamically changes the activation order of current sources to compensate for process variations, thereby maintaining linearity across the full output current range.
Solution Approach 2:
The patent implements preliminary action by performing sorting operations on current sources before actual signal conversion. The system pre-calibrates and determines the optimal switching sequences for all current sources in advance, storing these sequences for subsequent use during normal operation to ensure consistent linearity performance.
2Ease of operation
If signal transceiver circuit and DAC have different integral non-linearity trends in output step current, then device functionality is achieved, but echo cancellation performance deteriorates due to waveform mismatch between echo compensation signal and echo noise
Solution Approach 1:
The patent applies feedback by using the actual measured current levels from each current source to adjust the switching sequences. The system continuously monitors and adapts the switching patterns based on real performance data, ensuring that the DAC and echo canceller maintain matching INL trends for effective echo cancellation.
Solution Approach 2:
The patent implements asymmetry by applying different switching sequences to different current sources based on their individual characteristics. Instead of treating all current sources uniformly, the system assigns asymmetric switching patterns that compensate for each source's specific deviations, thereby aligning the overall INL trends between connected devices.
3Device complexity
If current sources are not properly calibrated, then device complexity is reduced, but noise generation increases due to mismatch between signal transceiver circuit and DAC
Solution Approach 1:
The patent applies self-service by implementing an automated calibration system that performs sorting operations and determines switching sequences without requiring manual intervention. The system automatically measures current levels, sorts the current sources, and generates optimal switching sequences, thereby reducing calibration complexity while effectively reducing noise through proper matching.
Data Source
AI summary
A method for calibrating currents includes performing a first sorting operation on a plurality of first current sources according to current levels generated by the first current sources, performing a second sorting operation on a plurality of second current sources according to current levels generated by the second current sources, determining a first switching sequence for the first plurality of current sources according to a result of the first sorting operation, and determining a second switching sequence for the second plurality of current sources according to a result of the second sorting operation and the first switching sequence. The plurality of first current sources have a same target current value, and the plurality of second current sources have a same target current value.