Switching Current Source Calibration Circuit
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Solution Overview
Problem
Conventional switching current sources suffer from errors due to mismatches between current sources, leading to voltage errors at the output node.
Innovation Solution
A circuit and method that utilize a programmable current source, calibrated using digital signals generated by a digital algorithm, to adjust the difference between currents from two current sources, with switches controlled by calibration signals to ensure matching currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sources are used without calibration, then the circuit structure is simple, but current mismatch errors occur leading to voltage errors at the output node
Solution Approach 1:
The patent applies preliminary action by performing current calibration before normal operation. A calibration circuit with switches is configured to connect current sources to a calibration node only during calibration mode, allowing current matching to be established in advance. This preliminary calibration action eliminates the need for continuous complex calibration circuits during operation, thus improving current matching precision while maintaining relatively simple circuit structure during normal operation.
Solution Approach 2:
The patent uses an intermediary approach by introducing a dedicated calibration node and calibration switches as intermediary elements. These intermediaries facilitate the calibration process by providing a temporary connection path between current sources and the calibration circuit, allowing current matching to be adjusted without affecting the main signal path. This intermediary mechanism enables precise current matching while keeping the main circuit structure simple.
2Measurement precision
If calibration circuits are added to reduce current mismatch, then current matching precision improves, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the calibration function into separate controllable segments. Different switches are used to selectively connect different current sources to the calibration node, allowing independent calibration of each current source. This segmented approach enables precise current matching through systematic calibration while keeping each calibration segment relatively simple and manageable.
Solution Approach 2:
The patent implements periodic action by performing calibration at specific intervals or under specific conditions rather than continuously. The calibration circuit is activated periodically or when needed, and normal operation proceeds without the calibration circuit active. This periodic calibration approach achieves current matching precision while minimizing the impact of calibration components on overall device complexity during normal operation.
Data Source
AI summary
In one embodiment the present invention includes circuits and methods for calibrating switching current sources. A difference between a source current and a sink current is detected during a calibration phase. The difference is used to generate a digital signal to adjust a programmable current source to reduce the difference between currents. In one embodiment, a binary search is used to generate the digital signal during an initial calibration phase, and a linear approximation is used to generate the digital signal during an operational calibration phase.