Output Transistor Gate Protection for Smaller Semiconductor Pads
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Solution Overview
Problem
The output-stage circuit of semiconductor devices requires large transistors to meet breakdown voltage specifications, leading to increased chip size.
Innovation Solution
The semiconductor device incorporates a pre-stage circuit with a signal transmitting portion and a voltage-breakdown protecting portion, utilizing smaller transistors for these functions, while the output-stage circuit uses a single-stage transistor to reduce terminal capacitance and chip size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large transistors are used in the output-stage circuit to meet breakdown voltage specifications, then voltage breakdown resistance is improved, but chip size increases
Solution Approach 1:
The patent segments the output-stage circuit into two independent paths: a high-voltage path with a first transistor having high breakdown voltage for meeting voltage specifications, and a low-voltage path with a second transistor having low breakdown voltage for reducing area. This segmentation allows each transistor to be optimized for its specific function, resolving the contradiction between breakdown voltage resistance and chip size.
Solution Approach 2:
The patent applies local quality by assigning different breakdown voltage characteristics to different parts of the circuit. The first transistor is designed with high breakdown voltage capability specifically for handling voltage spikes and ESD events, while the second transistor is designed with low breakdown voltage for efficient signal switching. This localized optimization allows the circuit to meet overall voltage requirements without requiring all transistors to be large.
2Reliability
If multiple transistors are used in the output-stage circuit to meet voltage specifications, then voltage breakdown resistance is improved, but terminal capacitance increases
Solution Approach 1:
The patent segments the output-stage circuit into two independent paths with different transistor characteristics. The first transistor handles high-voltage protection functions, while the second transistor handles low-voltage signal switching. This segmentation allows the signal path to use the low-capacitance second transistor, reducing overall terminal capacitance while maintaining voltage breakdown resistance through the first transistor.
Solution Approach 2:
The patent applies partial action by having the first transistor provide excessive voltage protection capability beyond what is needed for normal signal switching. This allows the second transistor to be optimized for minimal capacitance in the signal path, as the first transistor already provides sufficient voltage breakdown protection.
Data Source
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AI summary
A semiconductor device of the present invention includes: a P-type output transistor configured to have a source to which a power supply voltage is applied, and a drain connected to an external connection pad; a gate wiring configured to be connected to a gate of the output transistor; a signal transmitting portion configured to transmit an input signal to the gate wiring; and a voltage-breakdown protecting portion configured to apply the power supply voltage to a back gate of the output transistor if a voltage on the external connection pad is equal to or lower than the power supply voltage, or the voltage-breakdown protecting portion bringing the signal transmitting portion into a disconnection state and applies the voltage on the external connection pad to the gate and the back gate of the output transistor if the voltage applied on the external connection pad is higher than the power supply voltage.