Analog Switch Leakage Current Reduction via Substrate Potential Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor pressure sensors detect high-frequency ripple components, leading to reduced detection resolution and accuracy, especially at high temperatures, due to leakage currents in analog switches during low-cut-off frequency operations.
Innovation Solution
An improved analog switch design with N-channel and P-channel MOS FETs connected in parallel, where both transistors are formed within a common semiconductor substrate and maintained at a common reference voltage, eliminating external leakage currents and allowing for low-cut-off frequency switched-capacitor filters within integrated circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter with low cut-off frequency is used to remove high-frequency components, then detection accuracy is improved, but leakage current from analog switches increases at high temperatures
Solution Approach 1:
The patent changes the substrate potential parameter of the MOS FETs from a conventional fixed potential to a dynamically adjustable potential. By adjusting the substrate potential to match the potential of the connected node (input or output terminal), the potential difference across the switch is minimized, thereby reducing leakage current while maintaining low cut-off frequency filtering capability
Solution Approach 2:
The patent applies equipotentiality by setting the substrate potential of each MOS FET to be equal to the potential of the terminal it is connected to. This creates equipotential conditions that eliminate potential differences driving leakage current, allowing the analog switch to maintain low leakage even when operating with low cut-off frequencies that require longer switch on-times
2Measurement precision
If the cut-off frequency is reduced to filter high-frequency ripple, then detection resolution is improved, but the analog switch remains on longer causing increased leakage current
Solution Approach 1:
The patent dynamically changes the substrate potential parameter based on the operational requirements. When the analog switch needs to remain on for extended periods (low cut-off frequency operation), the substrate potential is adjusted to reduce the potential difference, thereby minimizing leakage current and energy loss while maintaining the necessary long on-time
3Measurement precision
If analog switches are used in switched-capacitor filters for low cut-off frequency, then high accuracy pressure sensing is enabled, but external leakage current flows at output terminal
Solution Approach 1:
The patent adjusts the substrate potential parameter of the MOS FETs to match the potential of the terminals they connect. This parameter change ensures that when the analog switch is off, there is no potential difference to drive external leakage current, enabling accurate pressure sensing in switched-capacitor filters operating at low cut-off frequencies
Solution Approach 2:
The patent creates equipotential conditions between the substrate and terminals by setting substrate potential equal to terminal potential. This eliminates the driving force for external leakage current at the output terminal, allowing the switched-capacitor filter to maintain high accuracy pressure sensing capability
Data Source
AI summary
An analog switch used in a switched capacitor filter has N-channel and P-channel MOS FETs connected in parallel between input and output switch terminals, with capacitor charge currents being periodically produced from the output terminal. The filter derives an output signal with respect to a reference voltage and maintains the switch input and output terminal at the reference voltage, while respective substrate potentials of the N-channel and P-channel MOS FETs are fixed at the reference voltage, so that the analog switch does not produce an external flow of leakage current that can affect the output signal of the filter during each interval when the switch is open.