Reference-Signal Track-and-Hold Calibration for ADC Resolution
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Solution Overview
Problem
Analog to digital converters face resolution degradation due to inherent nonlinearity in track and hold amplifiers, which impairs the accurate representation of analog input signals as digital signals.
Innovation Solution
The implementation of a track and hold amplifier with a voltage generating unit that provides a reference signal independent of the analog signal, coupled with switching circuits and capacitors, and a calibration processor to correct nonlinearity in the conversion process, ensuring accurate digital representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a track and hold amplifier is used in an A/D converter, then the analog signal can be tracked and held for accurate conversion, but the inherent nonlinearity of the amplifier degrades the resolution of the A/D converter
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before the actual conversion process. The system pre-characterizes the nonlinearity of the track and hold amplifier by measuring its transfer function at multiple known input levels, storing these calibration data for subsequent compensation during normal operation. This advance preparation eliminates the resolution degradation caused by nonlinearity without affecting the tracking and holding functionality.
Solution Approach 2:
The patent implements feedback by using the calibration measurements to generate correction factors that are applied to the conversion results. The system measures the actual output of the track and hold amplifier at known input levels, compares it with the expected linear output, and uses this feedback information to compensate for nonlinearity in subsequent conversions, thereby maintaining both tracking accuracy and resolution.
2Measurement precision
If calibration is performed to correct nonlinearity, then the resolution and accuracy are improved, but the device complexity and calibration time increase
Solution Approach 1:
The patent applies universality by designing the calibration circuit to perform multiple functions using the same hardware components. The switching network and capacitors used for signal routing during calibration are the same components used during normal conversion operations. The voltage generating unit that provides calibration voltages also serves as part of the normal converter architecture, eliminating the need for separate dedicated calibration hardware and reducing overall device complexity.
Solution Approach 2:
The patent uses parameter changes by varying the control signals to the switching circuits to reconfigure the capacitor network for different calibration modes. By changing the switching states and the voltages applied to capacitors, the system can perform multiple calibration measurements and corrections without changing the physical hardware configuration, thereby simplifying the device structure while maintaining calibration capability.
3Manufacturing precision
If multiple switching circuits and capacitors are used for calibration, then the nonlinearity compensation is more effective, but the device complexity and power consumption increase
Solution Approach 1:
The patent applies periodic action by performing calibration measurements at discrete intervals rather than continuously. The switching circuits are activated in periodic sequences to charge and discharge capacitors at specific timing points during the conversion process. This periodic operation allows effective nonlinearity compensation while minimizing the time that switching circuits and capacitors are active, thereby reducing power consumption compared to continuous calibration operations.
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 solution effectively calibrates the nonlinearity in track and hold amplifiers, enhancing the resolution and accuracy of analog to digital conversions by compensating for buffer nonlinearity through the use of reference signals and capacitors, resulting in a more precise digital output.
Implementation Method 1
Each of the switching circuits comprises a capacitor coupled between the first node and a second node
Data Source
AI summary
A track and hold amplifier is provided. The track and hold amplifier includes an input node receiving an analog signal, a buffer coupled between a first node and an output node, a first switch coupled between the input node and the first node, a plurality of switching circuits and a voltage generating unit. Each of the switching circuits includes a capacitor coupled between the first node and a second node. The voltage generating unit selectively provides a common signal or a reference signal to the capacitors of the switching circuits, wherein the reference signal is independent from the analog signal.