Bidirectional Analog Multiplexer Leakage Control
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Solution Overview
Problem
Existing analog multiplexers are not fully bidirectional and lack protection against high currents that can damage switching circuits, especially when operating in 'cold spare' mode with varying input and output voltages.
Innovation Solution
The design incorporates NMOS and PMOS switching modules with control modules that manage gate voltages and resistive circuits to ensure bidirectionality and protect against short circuits, using extended-drain transistors and diodes to handle high voltages with low drive voltages, and a voltage selection circuit to manage supply voltages effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional switching circuits are used in analog multiplexers, then the multiplexer can operate in cold spare mode with low power consumption, but the multiplexer cannot achieve full bidirectionality when input and output voltages vary
Solution Approach 1:
The patent implements dynamic voltage control of the switching circuits. The control module adjusts the gate voltage of the switching transistors based on the relative voltages at input and output terminals, enabling the switching circuit to adapt its operating state dynamically. This allows the multiplexer to achieve full bidirectionality while maintaining reliable operation under varying voltage conditions.
Solution Approach 2:
The patent changes the voltage parameter of the switching circuit to achieve bidirectionality. By applying different voltage levels to the gate of the switching transistor depending on whether the input voltage is higher or lower than the output voltage, the switching circuit can operate reliably in both directions. This parameter adjustment resolves the contradiction between bidirectionality and operation reliability.
2Reliability
If switching circuits operate without protection circuits, then device complexity is reduced, but high currents can flow and destroy the switching circuits
Solution Approach 1:
The patent introduces a control module as an intermediary between the input/output signals and the switching circuit. This control module monitors the voltage conditions and activates protection mechanisms only when necessary (during cold spare mode or abnormal conditions). By using this intermediary, the system achieves reliable protection against high currents while keeping the switching circuit simple during normal operation.
Solution Approach 2:
The patent implements preliminary protection by pre-configuring the switching circuit with protection capabilities that are activated only under specific conditions. The control module is designed to detect abnormal conditions in advance and activate protection mechanisms before high currents can damage the switching circuit, thus providing reliability without permanently increasing circuit complexity.
3Use of energy by moving object
If the multiplexer is configured for cold spare mode operation, then power consumption is minimized, but the multiplexer may be damaged by external signals at inputs or outputs
Solution Approach 1:
The patent extracts the protection function from the main switching circuit and implements it as a separate control module. During cold spare mode, the main switching circuit remains in a low-power state while the control module independently monitors for damaging conditions and activates protection only when needed. This separation allows the multiplexer to minimize power consumption while maintaining damage resistance.
Solution Approach 2:
The control module is pre-configured to detect abnormal voltage conditions at the inputs and outputs before they can damage the switching circuit. During cold spare mode, the control module remains in a low-power monitoring state and activates protection mechanisms only when damaging conditions are detected, thus providing reliability while minimizing power consumption during normal cold spare operation.
Data Source
AI summary
An analog multiplexer includes inputs and one output. A switching circuit is coupled between each input and the output. Each switching circuit includes an NMOS switching module, having an on state and an off state, and a control module supplied by a first supply voltage and operating to reduce leakage currents of the NMOS switching module when in the off state. The control module further operates to make the first NMOS switching module bidirectional irrespective of voltages present at the input and at the output.