Maximum Voltage Selection Circuit With Mode-Switched PMOS Output
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Solution Overview
Problem
Maximum voltage selection circuits in integrated circuits face challenges in selecting and outputting a maximum voltage effectively due to inadequate driving capacity of PMOS transistors when voltage differences are large, and failure to operate normally when voltage differences are small or voltages are the same.
Innovation Solution
A maximum voltage selection circuit with a peripheral signal circuit and a selection circuit that includes N sub-selection circuits, where each sub-selection circuit determines its operating mode based on an operating mode signal and sets its state as output enable while disabling other sub-selection circuits, using a PMOS transistor to output the maximum voltage when its input voltage is larger than a reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a PMOS transistor is used to output the maximum voltage in a maximum voltage selection circuit, then the circuit structure is simple, but the driving capacity is inadequate when voltage differences are small or voltages are the same
Solution Approach 1:
The maximum voltage selection circuit is divided into multiple sub-selection circuits (first sub-selection circuit, second sub-selection circuit, third sub-selection circuit, etc.), each responsible for comparing a specific input voltage with the reference voltage. This segmentation allows each sub-circuit to operate independently with enhanced driving capability while maintaining overall circuit functionality.
Solution Approach 2:
The circuit dynamically adjusts the operating mode of each sub-selection circuit based on the operating mode signal. When the operating mode signal indicates a need for enhanced driving capacity, the sub-selection circuits switch to a second operating mode that provides stronger driving capability, thereby adapting to different voltage difference conditions.
2Reliability
If a maximum voltage selection circuit is designed with multiple sub-selection circuits to enhance driving capability, then the driving capacity is improved, but the device complexity increases
Solution Approach 1:
Each sub-selection circuit is designed with multi-functionality, capable of operating in two different operating modes. The first operating mode provides standard functionality while the second operating mode enhances driving capacity. This universality allows the same circuit structure to serve multiple purposes, reducing overall complexity.
Solution Approach 2:
The circuit changes operational parameters (operating mode) based on the operating mode signal and voltage comparison results. By switching between different operating modes, the circuit can adjust its driving capacity dynamically without requiring completely different circuit structures for different conditions.
3Productivity
If the PMOS devices in the maximum voltage selection circuit are used when voltage differences are small, then the circuit operates in a compact mode, but the PMOS devices may not operate normally and cannot generate the output voltage
Solution Approach 1:
The circuit uses feedback through the operating mode signal to monitor the voltage comparison results and adjust the operating mode of each sub-selection circuit accordingly. When voltage differences are small, the feedback mechanism triggers a mode switch to ensure proper PMOS operation and reliable output voltage generation.
Solution Approach 2:
The circuit determines the operating mode in advance based on the operating mode signal before performing the voltage comparison and output generation. This preliminary action ensures that the PMOS devices are properly configured for the expected voltage conditions, preventing operational failures.
Data Source
AI summary
A maximum voltage selection circuit and method and a sub-selection circuit are provided. The maximum voltage selection circuit includes a peripheral signal circuit and a selection circuit with N channels of input voltages. The peripheral signal circuit provides an operating mode signal and a reference voltage to the selection circuit including N sub-selection circuits coupled to the N channels of input voltages respectively. A sub-selection circuit determines its operating mode according to the operating mode signal. In the operating mode, when an input voltage of a sub-selection circuit is larger than the reference voltage, the sub-selection circuit sets itself to the output enable state and sets other sub-selection circuits to the output disable state, and outputs its input voltage as a maximum voltage through a PMOS.