Multi-Channel Multiplexer Buffering for Low-Leakage Sensor Switching
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Solution Overview
Problem
In multiplexer systems, leakage current through disabled channels can distort sensor signals due to high output impedance of sensors, as even small leakage currents can generate significant voltages across disabled channels, altering the intended signal processed by the system.
Innovation Solution
Incorporating multiple metal oxide semiconductor field effect transistors (MOS transistors) with a bulk biasing circuit and a buffer to reduce leakage current, where the buffer couples the internal node of disabled channels to the output voltage level, maintaining a drain-to-source potential difference of approximately 0 V and minimizing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sensors are coupled to the multiplexer through multiple channels, then the system can process signals from multiple sensors, but leakage current through disabled channels distorts sensor signals due to high output impedance
Solution Approach 1:
A buffer circuit is introduced as an intermediary between the multiplexer output and the processing system. This buffer isolates the high-impedance sensor signals from the effects of leakage current in disabled channels, preventing signal distortion while maintaining multi-channel capability.
Solution Approach 2:
The patent applies bulk biasing to the MOS transistors in the multiplexer, changing the electrical parameters of the transistor channels. By adjusting the bulk voltage, the leakage current characteristics are modified to reduce the harmful effects on sensor signals during the off state.
2Ease of operation
If control signals disable remaining channels to process one sensor at a time, then signal processing is simplified, but leakage current through disabled channels generates significant voltages across high impedance sensors
Solution Approach 1:
The buffer circuit serves as a mediator that protects the high-impedance sensor nodes from voltage distortion caused by leakage current. It maintains signal integrity by isolating the sensor outputs from the multiplexer's disabled channels, allowing sequential processing without harmful voltage generation.
Solution Approach 2:
Bulk biasing modifies the electrical parameters of the MOS transistors to reduce leakage current magnitude. By changing the bulk voltage parameter, the transistor's off-state characteristics are improved, minimizing the voltage distortion that would otherwise occur across high-impedance sensor connections.
3Productivity
If MOS transistors are used as switches in the multiplexer, then channel switching is efficient, but leakage current flows through the transistor when the channel is off
Solution Approach 1:
Bulk biasing is applied to the MOS transistors to change their electrical parameters and reduce leakage current. By adjusting the bulk voltage, the transistor's off-state leakage characteristics are improved without affecting the on-state switching performance, thus maintaining high productivity while reducing energy loss.
Solution Approach 2:
The patent acknowledges that MOS transistors inherently have leakage current when off, but converts this harmful effect into a manageable parameter through bulk biasing. The leakage current is not eliminated but controlled to acceptable levels, allowing the efficient switching capability to be retained while minimizing energy loss.
Data Source
AI summary
A circuit includes a first switch assembly having a first input node and a first output node, and a second switch assembly having a second input node and a second output node. The circuit further includes a third switch assembly an operational amplifier, and a buffer. The third switch assembly has a third input node and a third output node. The third input node is coupled to the second output node, and the third output node is coupled to the first output node. The buffer has a buffer input and a buffer output. The buffer input is coupled to an input stage of the operational amplifier. The buffer output is coupled to the third switch assembly.