Interpolating DAC Error Correction for Integral Nonlinearity
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Solution Overview
Problem
High-resolution digital-to-analog converters (DACs) face significant nonlinearity errors due to the interpolation of voltages in multistage DACs, which limit their precision and accuracy, particularly in applications requiring high resolution such as computing and feedback control systems.
Innovation Solution
The implementation of error correction circuits within the interpolating circuit, utilizing voltage-current converter circuits with current sources and transistors, to minimize integral nonlinearity errors by adjusting currents and compensating for gate voltage differences between differential pairs connected to different voltages, thereby maintaining a nominal linear operating mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage interpolation is used in multistage DACs to achieve high resolution, then the effective resolution and accuracy are improved, but nonlinearity errors increase
Solution Approach 1:
The patent implements error correction circuits that use feedback mechanisms to detect and compensate for nonlinearity errors in the interpolation circuit. The correction circuits receive feedback about the actual output and adjust the interpolation to minimize integral nonlinearity error, thereby resolving the contradiction between achieving high resolution through interpolation and maintaining manufacturing precision.
Solution Approach 2:
The patent changes operating parameters by adjusting current levels in the interpolation circuit to optimize the linear operating mode. By modifying bias currents and operating points, the circuit achieves better linearity while maintaining the resolution benefits of interpolation, thus resolving the contradiction between measurement precision and manufacturing precision.
2Manufacturing precision
If error correction circuits are added to minimize nonlinearity errors, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the error correction functionality with the existing interpolation circuit structure by integrating correction circuits that share common elements such as current sources and transistors. This combining approach adds error correction capability while minimizing the increase in overall device complexity, as the correction functions are embedded within the existing circuit architecture rather than added as completely separate components.
3Manufacturing precision
If current adjustment is used to maintain linear operating mode, then manufacturing precision is improved, but energy consumption increases
Solution Approach 1:
The patent applies partial correction by using error correction circuits that adjust currents only to the extent necessary to minimize nonlinearity errors, rather than continuously maximizing correction. This partial action approach maintains the linear operating mode sufficiently to achieve the desired manufacturing precision while avoiding excessive energy consumption that would result from over-correction or continuous maximum correction effort.
Data Source
AI summary
Circuits and methods to minimize nonlinearity errors in interpolating circuits are described herein. A disclosed example circuit comprises first and second voltage-current converter circuits, each including a first transistor and a second transistor, each having a first electrode configured to receive a signal generated by a corresponding current source, a first current source providing a signal to the first voltage-converter circuit and comprising a first error correction circuit to minimize integral nonlinearity error in the interpolation circuit by setting a first current through the first current source to operate the first voltage-converter circuit in a nominal linear operating mode, and a second current source providing a signal to the second voltage-converter circuit and comprising a second error correction circuit to minimize integral nonlinearity error in the interpolation circuit by setting a second current through the second current source to operate the second voltage-converter circuit in the nominal linear operating mode.