Ternary Input Circuit Using Time-Division Switching for Stable Detection
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Solution Overview
Problem
Ternary value input circuits face issues with increased device area and unstable operation due to the need for setting desired threshold voltages in transistors, which also lead to complex designs and fluctuations in transistor threshold voltages.
Innovation Solution
A ternary value input circuit utilizing a pull-up switching device and a pull-down switching device, operated exclusively in time division, to control the connection and non-connection of the input terminal with power supplies, and incorporating a Schmitt trigger buffer and signal generator circuits to stabilize output states across three input terminal states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If threshold voltage is set at each transistor to detect input terminal states, then ternary value detection is achieved, but device area increases
Solution Approach 1:
The patent changes the detection parameter from transistor threshold voltage to RC time constant characteristics. By varying resistance values in the resistor network connected to the capacitive node, the circuit achieves ternary state detection without requiring precise threshold voltage setting in transistors, thereby reducing device area while maintaining detection precision.
2Measurement precision
If transistor threshold voltage is set for ternary detection, then output states vary with input states, but operation becomes unstable when threshold voltage fluctuates
Solution Approach 1:
The patent introduces a capacitive node and resistor network as intermediary elements between the input terminal and output inverters. This RC network acts as a mediator that converts input voltage states into distinct charging/discharging time constants, which are then detected by the inverters. This intermediary mechanism eliminates direct dependence on transistor threshold voltage, thereby stabilizing operation against threshold fluctuations.
3Measurement precision
If transistor threshold voltage is set for ternary detection, then detection is achieved, but design becomes complex
Solution Approach 1:
The patent simplifies the design by changing from voltage-threshold-based detection to time-constant-based detection. This parameter change eliminates the need for complex threshold voltage matching and compensation circuits, reducing design complexity while maintaining accurate ternary state detection through straightforward RC time constant control.
Data Source
AI summary
A pull-up switching device for controlling connection and non-connection of an input terminal IN and a first supply VDD and a pull-down switching device for controlling connection and non-connection of the input terminal IN and a second supply VSS are provided. The pull-up switching device and the pull-down switching device are operated exclusively on and off in time division to hold and output the state of the input terminal during each operating state from the two output terminals.