Capacitive ADC Pre-Charge Scheme for Low-Distortion Sampling
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Solution Overview
Problem
The increase in current drawn by the analog-to-digital converter affects the output signal of the programmable gain amplifier, leading to distorted signals and reduced signal-to-noise ratio (SNR) due to the high resolution requirements.
Innovation Solution
An analog-to-digital converting device and method that includes a capacitive digital-to-analog converter, comparator, and controller to generate and pre-charge voltages during specific periods, minimizing the difference between pre-charge and output voltages of the programmable gain amplifier, thereby reducing peak current draw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolution of the analog-to-digital converter is increased, then the measurement precision is improved, but the current drawn from the programmable gain amplifier increases causing signal distortion
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitive digital-to-analog converter to a pre-charge voltage during a pre-charge period before the actual sampling operation. This pre-charging action prepares the converter in advance, reducing the current surge that would otherwise be drawn from the programmable gain amplifier during sampling, thereby preventing signal distortion while maintaining high resolution capability
Solution Approach 2:
The patent introduces a pre-charge voltage as an intermediary between the power supply and the capacitive digital-to-analog converter. This intermediary voltage level serves as a buffer, allowing the converter to be prepared for sampling without directly drawing large currents from the programmable gain amplifier, thus mediating the harmful current draw effect
2Productivity
If the analog-to-digital converter draws more current, then the productivity is improved, but the signal-to-noise ratio is reduced due to output signal distortion
Solution Approach 1:
The pre-charging operation performed in advance during the pre-charge period enables the capacitive digital-to-analog converter to be ready for rapid sampling without causing current surges. This preliminary preparation maintains high sampling speed while preserving signal integrity and signal-to-noise ratio by avoiding the distortion that would result from excessive current draw
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 approach reduces the impact on the programmable gain amplifier's output, preventing distorted signal sampling and improving the signal-to-noise ratio.
Implementation Method 1
a capacitive digital-to-analog converter is configured to respectively generate a first sample voltage and a second sample voltage according to a non-inverting output voltage and an inverting output voltage
Implementation Method 2
a comparator is configured to generate a comparing signal by comparing the first sample voltage and the second sample voltage
Data Source
AI summary
An analog-to-digital converting device includes a capacitive digital-to-analog converter, a comparator, and a controller. The capacitive digital-to-analog converter respectively generates a first and a second sample voltage according to a non-inverting output voltage and an inverting output voltage of a programmable gain amplifier during a sample period. The comparator generates a comparing signal by comparing the first and the second sample voltages during a converting period. The controller controls the capacitive digital-to-analog converter to generate a converting voltage according to the comparing signal during the converting period. The controller controls the capacitive digital-to-analog converter such that the capacitive digital-to-analog converter is pre-charged to a pre-charge voltage during a pre-charge period. The pre-charge voltage is between a maximum value and a minimum value of the non-inverting output voltage and the inverting output voltage of the programmable gain amplifier.