DAC Transfer Function Calibration via Node-Selective Trim Currents
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) face challenges in achieving accurate analog output due to manufacturing variances and non-linearities in resistor values, leading to voltage errors and non-linearity in the transfer function.
Innovation Solution
A digital-to-analog converter comprising an impedance network and a transfer function modification circuit, which includes a trim current DAC and a demultiplexer. The demultiplexer selectively connects the output of the DAC to different nodes of the impedance network, allowing for the injection of positive or negative currents to modify the transfer function post-manufacture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If resistor networks are used in DACs to generate voltage values, then the DAC can convert digital codes to analog voltages, but manufacturing variances and resistor tolerances cause voltage errors and non-linearity
Solution Approach 1:
A trim current DAC and demultiplexer are introduced as intermediary components. The trim current DAC generates correction currents that are injected into specific nodes of the impedance network via the demultiplexer. This intermediary correction mechanism compensates for voltage errors caused by resistor variations without requiring higher precision resistors.
Solution Approach 2:
The invention changes the electrical parameters of the impedance network nodes by injecting trim currents. By modifying the current at each node, the voltage values are adjusted to correct non-linearity and errors in the transfer function, effectively compensating for manufacturing variations in the resistor network.
2Measurement precision
If resistor tolerances and process variations are reduced to improve accuracy, then voltage errors decrease, but manufacturing complexity and cost increase
Solution Approach 1:
The invention converts the harmful effect of resistor variations into a beneficial correction process. Instead of trying to eliminate variations through tighter tolerances, the system measures the actual voltage errors and injects compensating trim currents to correct them, turning manufacturing imperfections into an opportunity for post-fabrication optimization.
3Measurement precision
If a trim current DAC and demultiplexer are added to modify the transfer function, then voltage accuracy and linearity improve, but device complexity increases
Solution Approach 1:
The trim current DAC and demultiplexer serve multiple functions: they correct voltage errors, adjust the transfer function, and enable post-fabrication calibration. This multi-functionality justifies the added complexity by providing comprehensive error correction capabilities that improve overall DAC accuracy.
4Measurement precision
If post-manufacture transfer function modification is enabled, then accuracy is improved, but calibration time and process complexity increase
Solution Approach 1:
The trim current DAC and demultiplexer are pre-configured to enable post-fabrication calibration. By having the correction infrastructure in place before final assembly, the system allows for efficient calibration processes that can be performed automatically, reducing the time and complexity of the calibration process compared to manual adjustment methods.
Data Source
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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.