Segmented Ramp Sampling Circuits for Accurate Level-Crossing Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Sample-data circuits face challenges in maintaining accurate output voltages due to difficulties in achieving sufficient open-loop gain, low noise, and fast settling times, especially with low power supply voltages and device gain, which leads to errors and suboptimal performance parameters like speed, accuracy, and power consumption.
Innovation Solution
The implementation of a zero-crossing detector and waveform generator in sample-data circuits that use differential signal paths and generate ramp waveforms with linear segments of varying slopes, allowing for precise timing of voltage sampling and minimizing errors caused by delays, while optimizing performance parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If operational amplifiers are designed to provide sufficient open-loop gain and fast settling time, then output voltage accuracy is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The virtual ground node voltage is restored to ground level at the beginning of each sampling phase before the sampling capacitor is switched. This preliminary action ensures that the node is ready for accurate sampling without requiring the operational amplifier to maintain ground level continuously, reducing power consumption while preserving accuracy when needed.
Solution Approach 2:
The operational amplifier only needs to maintain the virtual ground node at ground level during specific sampling intervals rather than continuously. The circuit periodically restores the node voltage to ground at the start of each sampling phase, allowing the op-amp to operate at lower power between sampling events while maintaining accuracy during critical measurement moments.
2Measurement precision
If operational amplifiers are designed to provide sufficient open-loop gain and fast settling time, then output voltage accuracy is improved, but device complexity increases
Solution Approach 1:
The circuit automatically restores the virtual ground node voltage to ground level at the beginning of each sampling phase through a dedicated restoration circuit. This preliminary action simplifies the operational amplifier design requirements, as the op-amp only needs to maintain ground level during sampling intervals rather than continuously, reducing design complexity while preserving accuracy.
3Measurement precision
If the voltage at the virtual ground node is maintained precisely at ground all the time, then output voltage accuracy is improved, but power consumption increases
Solution Approach 1:
The virtual ground node voltage is maintained at ground level only during sampling intervals when accuracy is critical, rather than continuously. A restoration circuit periodically resets the node voltage to ground at the start of each sampling phase, allowing the circuit to consume less power during non-sampling periods while maintaining accuracy when needed.
Solution Approach 2:
The restoration circuit proactively resets the virtual ground node voltage to ground level at the beginning of each sampling phase before the actual sampling occurs. This preliminary restoration ensures accuracy is ready when needed without requiring continuous power consumption to maintain the ground level.
4Speed
If delays in detectors are reduced to improve speed, then sampling accuracy is improved, but the circuit becomes more sensitive to timing errors
Solution Approach 1:
The virtual ground node is restored to ground level at the beginning of each sampling phase before the sampling capacitor is switched. This preliminary restoration ensures that even with detector delays, the node is already at the correct voltage level when sampling occurs, maintaining accuracy while allowing faster operation.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A sample-data analog circuit includes a level-crossing detector. The level- crossing detector controls sampling switches to provide a precise sample of the output voltage when the level-crossing detector senses the predetermined level crossing of the input signal. A multiple segment ramp waveform generator is used in the sample-data analog circuits. The ramp waveform generator includes an amplifier, a variable current source, and a voltage detection circuit coupled to the current source to control the change in the amplitude of the current. The ramp generator produces constant slope within each segment regardless of the load condition. The sample-data analog circuit also utilizes variable bandwidths and thresholds.