Segmented Ramp Circuits With Level-Crossing Sampling Accuracy
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Solution Overview
Problem
Sample-data circuits face challenges in maintaining accurate output voltages due to delays and noise, particularly at the virtual ground node, which affects speed, accuracy, and power consumption, especially under low power supply voltages and scaled device gain.
Innovation Solution
Incorporating a level-crossing detector and a waveform generator with a switching circuit to generate positive and negative slope waveforms, and using a zero-crossing detector with a bandwidth controller to optimize sampling and reduce errors caused by delays, while providing differential signal paths for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If operational amplifiers are used to process signals in sample-data circuits, then signal processing capability is improved, but maintaining accurate output voltage becomes difficult due to delays and noise
Solution Approach 1:
A dummy switch is introduced as an intermediary element that replicates the switching action of the main switch. This dummy switch operates in parallel and generates a delayed signal that compensates for the delay introduced by the main switch, thereby maintaining output voltage accuracy without sacrificing speed.
Solution Approach 2:
The dummy switch is configured to anticipate and compensate for the delay that will occur in the main switch. By pre-adjusting the timing or phase of the dummy switch operation, the system counteracts the expected delay before it affects the output voltage, maintaining accuracy proactively.
2Adaptability or versatility
If operational amplifiers provide large output swing for high dynamic range, then signal range is improved, but maintaining virtual ground node at correct level becomes difficult under low power supply voltages
Solution Approach 1:
The dummy switch acts as a mediator that balances the voltage fluctuations at the virtual ground node. By replicating the switching disturbance, it enables the operational amplifier to maintain large output swing while the dummy switch's compensating action keeps the virtual ground node voltage stable, even under low power supply conditions.
3Productivity
If switches are used for sampling in switched-capacitor integrators, then signal sampling capability is improved, but errors are introduced due to switch delays
Solution Approach 1:
The dummy switch serves as a mediator that replicates the timing characteristics of the main sampling switch. By creating a parallel switching path with matched delay characteristics, the dummy switch enables accurate compensation of sampling errors while maintaining high sampling speed through the primary switch.
Data Source
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.