Tristate Output Buffer Gate Isolation for Wide-Voltage Leakage Control
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Solution Overview
Problem
Existing gate control circuits face challenges in supporting a wide voltage range, particularly with the need for low voltage operation, as they struggle to maintain reliability and minimize leakage while handling voltages from 0.65 V to 3.6 V, leading to inefficiencies and increased complexity.
Innovation Solution
A gate control circuit with a gate isolation switch that allows shared pull-up and pull-down transistors for control signals VP and VN, utilizing a combination of low VT and standard VT transistors in parallel to optimize voltage handling and minimize leakage, along with a gate isolation switch that keeps the output in a high impedance state during power-up, simplifying the circuit design and reducing die area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pull-up and pull-down circuits are used for control signals VP and VN, then the output can be reliably controlled, but the circuit complexity and die area increase
Solution Approach 1:
The patent combines the pull-up and pull-down control circuits into a shared configuration where transistors M2-M5 are commonly used for both control signals VP and VN. This merging reduces the total number of transistors from what would be required for completely separate circuits, thereby reducing die area and circuit complexity while maintaining reliable output control through the gate isolation switch.
2Area of stationary object
If the gate control circuit is kept simple with shared transistors, then die area is reduced, but static leakage current increases
Solution Approach 1:
The gate isolation switch acts as an intermediary element that controls the connection between the shared pull-up/pull-down circuits and the output. When the output buffer is not in use, the gate isolation switch disconnects the control signals VP and VN from the shared transistors M2-M5, preventing static leakage current while maintaining the area benefits of the shared circuit configuration.
3Use of energy by moving object
If the output buffer is disabled to reduce power consumption, then energy efficiency improves, but the circuit requires additional control mechanisms
Solution Approach 1:
The gate isolation switch serves multiple functions: it controls the enabling/disabling of the output buffer for power management, maintains high impedance state when disabled, and works in conjunction with the shared pull-up/pull-down circuits. This multi-functionality achieves power savings without requiring separate dedicated control circuits, thereby avoiding additional complexity.
4Adaptability or versatility
If low voltage operation is supported to meet future requirements, then adaptability improves, but leakage control becomes more difficult
Solution Approach 1:
The circuit employs dynamic control through the gate isolation switch that can adapt its state based on operating conditions. The switch enables the circuit to dynamically transition between active and high-impedance states, allowing the gate control circuit to maintain low leakage performance across a wide voltage range from 0.65V to 3.6V by disconnecting unused pathways regardless of the specific voltage level.
Data Source
AI summary
A gate control circuit for a tristate output buffer operating in a first voltage domain includes a pull-up circuit coupled between an upper rail and a first gate control signal, a pull-down circuit coupled between a lower rail and a second gate control signal, and a gate isolation switch coupled between the first gate control signal and the second gate control signal. The gate isolation switch includes a first PMOS transistor coupled in parallel with a first NMOS transistor. The first NMOS transistor is controlled by a first enable signal and the first PMOS transistor is controlled by a second enable signal.