Calibrated DAC Current Source Sequencing to Reduce Output Ripple
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Solution Overview
Problem
High precision digital-to-analog converters (DACs) face challenges in producing identical current sources due to manufacturing variances and noise levels, especially as integrated circuits shrink, leading to difficulties in achieving accurate calibration and output precision.
Innovation Solution
The implementation of a method and apparatus that includes a digital-to-analog converter with a plurality of current sources, a calibrator, and a current source selector, where the current sources are calibrated sequentially and assigned to digital bits in a synchronized bit-to-current source sequence to reduce current errors and ripple in the analog output, using a substitute current source to maintain operation during calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current sources are calibrated sequentially during operation, then output precision is improved, but current errors and ripple in the analog output increase
Solution Approach 1:
The patent applies preliminary action by pre-establishing a bit-to-current source assignment sequence that is synchronized with the calibration sequence. This predetermined assignment strategy anticipates the calibration process and configures current source allocation in advance to minimize ripple and current errors during calibration, thereby resolving the contradiction between maintaining precision and reducing harmful effects.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the bit-to-current source assignment based on the calibration sequence. The assignment is not static but changes in synchronization with the calibration process, allowing the system to adapt current source allocation to the ongoing calibration state, thus reducing ripple and current errors while maintaining output precision.
2Volume of moving object
If manufacturing precision is reduced due to smaller integrated circuits, then device scaling is achieved, but current source identity and calibration accuracy deteriorate
Solution Approach 1:
The patent applies feedback by implementing a calibration process that measures actual current source values and uses this information to adjust assignments. The calibration sequence provides feedback about current source variations, and the synchronized bit-to-current source assignment uses this feedback to compensate for manufacturing tolerances, thereby maintaining current source identity despite smaller circuit dimensions.
Solution Approach 2:
The patent implements parameter changes by dynamically changing the assignment parameters (which current source is assigned to which bit) based on calibration results. This allows the system to adjust operational parameters to compensate for manufacturing variations, maintaining accuracy despite reduced manufacturing precision in smaller integrated circuits.
Data Source
AI summary
Methods and apparatus for error cancelation in calibrated current sources are disclosed. In an example, a digital to analog converter to convert digital bits into an analog output signal is described, including a plurality of current sources, a calibrator, and a current source selector. The example current sources output substantially identical currents, and the calibrator is selectively coupled to sequentially calibrate the current sources to a reference current. The example current source selector assigns respective ones of the plurality of current sources to the digital bits in accordance with a bit-to-current source sequence selected to reduce current error in the analog output and changes the assignments based on the current source coupled to the calibrator.