High-Voltage Bus Holder Circuit Without Static Current
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Solution Overview
Problem
Conventional high voltage tolerant bus holder circuits consume static current, are not suitable for low power applications, and require additional processing steps, increasing manufacturing costs, while failing to effectively manage voltage thresholds and prevent gate-oxide stress.
Innovation Solution
A high voltage tolerant bus holder circuit utilizing two series-connected PMOS pull-up transistors, two series-connected NMOS pull-down transistors, and two parallel-connected control transistors, configured to switch between pull-up and pull-down modes without static current consumption, and realizable in baseline CMOS process technology without additional manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional high voltage tolerant bus holder circuits are used to interface with different voltage systems, then voltage compatibility is improved, but static current consumption increases
Solution Approach 1:
The circuit dynamically adjusts the operating state of transistors based on bus voltage conditions. Control transistors switch between active and inactive states depending on whether the bus voltage exceeds the threshold, enabling the circuit to adapt between high voltage tolerance mode and low power consumption mode, thus resolving the contradiction between voltage compatibility and static current consumption
Solution Approach 2:
The circuit changes the electrical parameters (conductance state) of transistors based on the bus voltage level. When voltage exceeds the threshold, control transistors modify the conductance of pull-up and pull-down transistors to prevent excessive current flow, thereby maintaining voltage compatibility while reducing static current consumption
2Reliability
If conventional high voltage tolerant bus holder circuits are designed with additional protection transistors, then voltage tolerance is improved, but device complexity increases
Solution Approach 1:
The control transistors serve multiple functions simultaneously: they act as switches to enable/disable pull-up and pull-down transistors, provide voltage threshold detection, and protect against excessive voltage stress. This multi-functionality achieves high voltage tolerance without proportionally increasing device complexity
Solution Approach 2:
The control transistors act as intermediary elements between the bus and the pull-up/pull-down transistors. They mediate the voltage interaction by selectively connecting or disconnecting the main transistors based on voltage conditions, providing protection while maintaining a relatively simple circuit structure
3Adaptability or versatility
If the bus holder circuit uses additional processing steps to achieve high voltage tolerance, then voltage compatibility is improved, but manufacturing cost increases
Solution Approach 1:
The circuit achieves voltage compatibility through parameter control (gate voltage control of transistors) rather than requiring special processing steps. By dynamically adjusting transistor operating parameters based on bus voltage, the circuit attains high voltage tolerance using standard CMOS fabrication processes, thereby reducing manufacturing costs
Data Source
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AI summary
A high voltage tolerant bus holder circuit (100) and method of operating the bus holder circuit utilizes first and second control transistors (110,112) connected in parallel between a control terminal (VX) of a pull-up transistor (104) and a bus (118). The first control transistor (110) is used to turn on the pull-up transistor (104) during a pull-up mode of operation. The second control transistor (112) is used to turn off the pull-down transistor (106) when a voltage on the bus exceeds a threshold.