DAC Transfer Function Calibration via Selective Node Current Injection
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) suffer from non-linearities due to manufacturing variances and parasitic impedances, leading to inaccuracies in voltage outputs, which conventional calibration methods struggle to address effectively.
Innovation Solution
A digital-to-analog converter system incorporating a demultiplexer to selectively connect the output of a current DAC to different nodes of the impedance network, allowing post-manufacture configuration of current injection or drainage to modify the transfer function, thereby improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods are used, then manufacturing costs are reduced, but DAC accuracy and linearity are insufficient due to resistor variations and parasitic impedances
Solution Approach 1:
The patent introduces a trim current DAC and demultiplexer as intermediary components that inject calibration currents into specific nodes of the impedance network. This mediator approach allows external or separate calibration circuitry to compensate for manufacturing errors without requiring complex integrated calibration mechanisms within the main DAC path, thereby improving accuracy while controlling complexity.
Solution Approach 2:
The patent modifies the electrical parameters (current values) injected into the impedance network nodes through the trim current DAC to compensate for manufacturing-induced non-linearities. By changing these current parameters dynamically during calibration, the system achieves improved transfer function linearity without permanently altering the physical structure of the main DAC components.
2Manufacturing precision
If resistor tolerances and process variations are reduced, then DAC linearity improves, but manufacturing cost and difficulty increase
Solution Approach 1:
The patent converts the harmful effect of resistor manufacturing variations into a benefit by using these same variations as calibration reference points. The trim current DAC measures and compensates for the actual non-linearities introduced by manufacturing tolerances, turning what would be a defect into an opportunity for post-manufacturing optimization, thereby achieving high accuracy with standard-tolerance components.
Solution Approach 2:
The patent performs preliminary characterization of the impedance network's non-linearities during manufacturing or initial operation, storing this information for use during calibration. By预先 measuring and storing the specific deviation patterns of each device, the system can apply targeted compensation without requiring expensive tight-tolerance components, as the preliminary data guides the calibration process.
3Adaptability or versatility
If multiple calibration nodes are accessible, then transfer function modification flexibility increases, but device complexity and area increase
Solution Approach 1:
The patent implements a universal calibration architecture where a single trim current DAC and demultiplexer can calibrate multiple nodes of the impedance network. The demultiplexer routes the calibration current to different nodes based on which node requires adjustment, making one calibration circuit perform the function of multiple dedicated calibration circuits would otherwise be needed, thereby reducing area while maintaining flexibility.
Solution Approach 2:
The patent segments the calibration function into two separate components: a trim current DAC that generates the calibration current, and a demultiplexer that routes it to the appropriate node. This segmentation allows the calibration system to service multiple nodes sequentially through a single current source, reducing the total area required compared to having separate current sources for each node, while still providing access to multiple calibration points.
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 enhances DAC accuracy by enabling flexible, economical compensation for manufacturing-induced errors, reducing non-linearities and improving the overall performance of the DAC system.
Implementation Method 1
the trim current DAC is configured to modify the transfer function of the DAC by injecting current into, or draining current from, a selected node of the plurality of nodes via a selected output of the demultiplexer
Data Source
AI summary
The present disclosure relates to a digital-to-analog converter comprising an impedance network and a transfer function modification circuit. The transfer function modification circuit comprises a DAC and a demultiplexer. The demultiplexer may be used to selectively connect the output of the DAC to different respective nodes of the impedance network, allowing positive or negative currents to be injected into the node and modify the transfer function. By using a demultiplexer to selectively couple to different nodes, the node into which the current is injected may be modified post-manufacture, allowing transfer function modification.