DAC Current Source Measurement for Linearity Offset Correction
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Solution Overview
Problem
Current digital-to-analog conversion apparatuses with current output suffer from process variations leading to non-ideal amplitude and shape offsets, reducing system efficiency.
Innovation Solution
A digital-to-analog conversion apparatus and method incorporating a digital-to-analog conversion circuit with thermometer-controlled current sources, an echo transmission circuit, an echo-canceling circuit, and a current calculation circuit, utilizing two specific input codewords to control the operation status of current sources to generate analog signals with opposite signs and identical absolute values, and calculating current amounts using converged echo-canceling coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current output digital-to-analog conversion is used, then the conversion function is achieved, but process variation causes non-ideal amplitude and shape offsets reducing system efficiency
Solution Approach 1:
The patent implements an echo-canceling circuit that generates echo-canceling signals based on echo-canceling coefficients, continuously adjusting to cancel echo signals. This feedback mechanism allows the system to adapt to process variations and compensate for current offsets, thereby improving current output accuracy while maintaining system efficiency
Solution Approach 2:
The patent replaces traditional mechanical calibration methods with an electronic signal processing approach. By using echo transmission and echo-canceling circuits to generate and process test signals, the system electronically measures and compensates for current source characteristics, eliminating the need for manual calibration and reducing the impact of process variations
2Manufacturing precision
If current source offsets are not compensated, then device complexity is low, but amplitude and shape offsets reduce conversion precision
Solution Approach 1:
The patent designs the echo transmission circuit and echo-canceling circuit to serve multiple functions: they generate test signals, measure current source characteristics, and compensate for offsets. This multi-functionality allows precise current conversion without adding significant circuit complexity, as the same circuits perform multiple tasks in the calibration and operation phases
Solution Approach 2:
The system performs self-calibration by automatically measuring its own current source characteristics through echo signals and adjusting echo-canceling coefficients accordingly. This self-service mechanism eliminates the need for external calibration equipment or complex manual adjustment circuits, achieving high precision while keeping the device complexity manageable
Data Source
AI summary
The present invention discloses a digital-to-analog conversion apparatus having current source measuring mechanism. A digital-to-analog conversion circuit in turn sets one of thermo-controlled current sources as an initial current source to operate according to two specific input codewords included in an input digital signal to generate an output analog signal. The values of the output analog signal corresponding to the two specific input codewords have opposite signs and the same absolute value. An echo transmission circuit processes the output analog signal to generate an echo signal. An echo-canceling circuit processes the input digital signal according to echo-canceling coefficients to generate an echo-canceling signal and receives an error signal to converge the echo-canceling coefficients. A current calculating circuit generates converged coefficients statistics values and perform calculation thereon with a predetermined inverse matrix to generate a current amount of each of the thermo-controlled current sources. An error calculation circuit subtracts the echo signal and the echo-canceling signal to generate the error signal.