Gate-Overbiased I/O Driver Transistors for High-Voltage Pads
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Solution Overview
Problem
High-voltage exposure at I/O pads in integrated circuits (ICs) leads to performance issues due to the use of thick-oxide transistors, which add significant capacitance and weaken drive currents, making it difficult to meet performance requirements for semiconductor technology nodes.
Innovation Solution
The implementation of gate overbiased, thick gate oxide (GO-TGX) transistors with reduced channel length and increased gate oxide thickness, which provide reduced capacitance and high drive currents while maintaining tolerance to high gate-to-source voltages, replacing conventional thick-oxide devices in output drivers for I/O circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick-oxide transistors are used to protect circuits from high voltages at I/O pads, then voltage protection is improved, but capacitance increases and drive current weakens
Solution Approach 1:
The transistor is segmented into two distinct types: thick-oxide transistors for voltage protection functions and thin-oxide transistors for high-speed drive functions. This segmentation allows each transistor type to be optimized for its specific function without compromise, resolving the contradiction between protection and performance.
Solution Approach 2:
Different oxide thicknesses are applied to different transistors based on their functional requirements. Thick-oxide transistors are used specifically where voltage protection is needed, while thin-oxide transistors are used where high drive current and low capacitance are required, achieving local optimization of properties.
2Reliability
If thick-oxide transistors are used to protect circuits from high voltages at I/O pads, then voltage protection is improved, but drive current weakens
Solution Approach 1:
The transistor system is segmented into protection transistors (thick-oxide) and drive transistors (thin-oxide), allowing the drive transistors to deliver high current while protection transistors handle voltage stress, thus resolving the contradiction between protection and drive capability.
Solution Approach 2:
Thin-oxide transistors are strategically placed in positions requiring high drive current, while thick-oxide transistors are positioned where voltage protection is critical, optimizing both protection and drive performance simultaneously.
3Reliability
If conventional thick-oxide devices are used in output drivers, then voltage tolerance is improved, but capacitance increases by 20-30%
Solution Approach 1:
The output driver is segmented into voltage protection elements using thick-oxide transistors and high-speed switching elements using thin-oxide transistors, eliminating the need for universally thick-oxide devices and reducing overall capacitance by 20-30%.
Solution Approach 2:
The oxide thickness parameter is changed from uniform thick-oxide to a mixed configuration with both thick and thin oxide regions, optimized according to local functional requirements, thereby reducing total capacitance while maintaining voltage tolerance.
Data Source
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AI summary
An electronic circuit and methods of operating the electronic circuit are provided. The electronic circuit includes a pull-up transistor for pulling up an input/output (I/O) node of the output circuit to a first voltage and a first isolation transistor for coupling the pull-up transistor to the I/O node. The electronic circuit also includes a pull-down transistor for pulling down the I/O node to a second voltage and a second isolation transistor for coupling the pull-down transistor to the I/O node. In the electronic circuit, the pull-up and the pull-down transistors are transistors supporting a first drain-to-source voltage and a first gate-to-source voltage, while the first and the second isolation transistors are transistors supporting the first drain-to-source voltage and a second gate-to-source voltage greater than the first gate-to-source voltage.