Zero-Crossing Detector Calibration for Low-Power Sampled-Data Circuits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Operational amplifiers in switched-capacitor circuits face challenges in achieving accurate integration and low noise due to low power supply voltages and device gain limitations, leading to difficulties in maintaining precise output voltages and high dynamic range, especially in scaled technologies.
Innovation Solution
The implementation of zero-crossing detectors in switched-capacitor circuits, which detect the zero-crossing point of the voltage at the virtual ground node to sample the output voltage accurately, reducing the need for constant operational amplifier performance and allowing for efficient offset cancellation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If operational amplifiers are designed to provide sufficient open-loop gain and fast settling time for accurate integration, then measurement precision is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing offset cancellation during a dedicated calibration phase before normal operation. The offset voltage is sampled and stored on a cancellation capacitor during calibration, then this pre-computed offset value is used to compensate for offset errors during signal processing, eliminating the need for continuous high-power operational amplifier operation.
Solution Approach 2:
The patent extracts the offset voltage component from the signal path by sampling it separately during calibration and storing it on a dedicated offset cancellation capacitor. This separated offset representation can then be subtracted from the signal path independently, allowing the main operational amplifier to operate at lower power while maintaining accuracy.
2Measurement precision
If operational amplifiers are designed to provide large output swing for high dynamic range, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary offset measurement and cancellation during a calibration phase, storing the offset value on a cancellation capacitor. This pre-processing of offset information simplifies the operational amplifier design during signal processing, as the amplifier no longer needs to maintain precise zero-offset under all conditions, reducing design complexity while preserving dynamic range.
3Measurement precision
If the voltage at the virtual ground node is maintained precisely at ground all the time, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent implements periodic action by maintaining the virtual ground node at precise ground potential only during calibration phases when offset sampling occurs, rather than continuously during all operation. During normal signal processing, the offset cancellation capacitor handles offset compensation, allowing the virtual ground to operate with relaxed precision requirements, thereby reducing power consumption while maintaining measurement accuracy when needed.
Data Source
AI summary
A zero-crossing detector with effective offset cancellation includes a set of series connected capacitors and an amplifier having an input terminal. An offset capacitor is operatively connected between the amplifier and the set of series connected capacitors. A switch is operatively connected to the input terminal, and an offset sampling capacitor is operatively connected to the switch. The switch connects the offset sampling capacitor to the input terminal of the amplifier during a charge transfer phase.