Center-Tap T-Switch Biasing for Low-Leakage ADC Sampling
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Solution Overview
Problem
Current electronic switches, particularly in analog to digital converters (ADCs), experience current leakage when in the off mode, leading to errors in digital code conversion due to voltage differentials, which is exacerbated in multi-channel ADCs and complicates the implementation of high-accuracy and high-input-channel ADCs.
Innovation Solution
A t-switch configuration with a bias voltage generation circuit (BVGC) that reduces voltage differential between the output and center-tap ports, implemented using sub-switches and control logic to manage the connection and disconnection of voltage sources, effectively minimizing current leakage by applying a bias voltage to the center-tap port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a t-switch is used to selectively connect voltage input to ADC input, then the ADC can sample multiple voltage sources, but current leakage occurs due to voltage differential causing conversion errors
Solution Approach 1:
The patent applies equipotentiality by connecting the center-tap port to the midpoint between input and output ports through sub-switches. This creates equal potential paths, reducing voltage differential across the t-switch. When the center-tap is connected to the midpoint, the voltage at the center-tap port becomes approximately half the input voltage, minimizing the voltage differential that causes current leakage, thereby maintaining measurement precision while preserving multi-channel selection capability.
Solution Approach 2:
The patent introduces an intermediary element - the center-tap port with its associated sub-switches - between the input and output ports. This intermediary provides a controlled connection path that balances the voltage potential, acting as a mediator to reduce the harmful voltage differential. The center-tap port serves as an intermediate node that can be selectively connected to the midpoint, providing a controlled pathway that minimizes current leakage while maintaining signal integrity.
2Measurement precision
If two-stage input sampling is used to solve leakage problem, then current leakage is reduced, but device complexity and surface area increase due to requiring two sets of sampling networks
Solution Approach 1:
The patent segments the t-switch into three sub-switches (first, second, and third sub-switches) controlled by independent control signals. This segmentation allows selective connection of the center-tap port to different nodes (input port, output port, or midpoint) based on operational requirements. By dividing the switching function into controllable segments, the patent achieves leakage reduction without requiring a complete two-stage sampling network, thus reducing device complexity while maintaining conversion accuracy.
Solution Approach 2:
The patent implements dynamic control of the t-switch configuration through multiple control signals that can independently regulate the state of each sub-switch. This dynamic capability allows the system to adaptively switch between different connection modes (center-tap connected to input, output, or midpoint) based on the operational phase, enabling leakage reduction during critical sampling periods while maintaining flexibility for other operations, avoiding the static complexity of two-stage networks.
3Measurement precision
If the ADC conversion time is extended to improve accuracy, then more precise digital code is obtained, but current leakage has more time to deplete sampled charge
Solution Approach 1:
The patent applies preliminary anti-action by proactively reducing the voltage differential through center-tap connection to the midpoint before the ADC conversion process begins. By minimizing the voltage differential that drives current leakage in advance, the system prevents charge depletion during the conversion period. This preliminary protective action allows the ADC to take its time for accurate conversion without worrying about significant charge loss, effectively decoupling conversion time from charge depletion concerns.
Data Source
AI summary
An apparatus is provided comprising a first t-switch, which includes an input port arranged to be connected to a first voltage source, a center-tap port, and an output port arranged to be connected to a load. The first t-switch is configured to connect the input port to the output port in an on mode and disconnect the input port from the output port in an off mode. The apparatus further comprises a bias voltage generation circuit configured to generate a bias voltage, the generated bias voltage coupled to the center-tap port of the first t-switch, the bias voltage determined based upon an output port voltage.