Wide-Voltage Output Interface Using De-MOS and Level Shifting
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Solution Overview
Problem
Integrated circuit (IC) designs face challenges in handling high-voltage applications without subjecting low-voltage thin-film transistors to voltage stress, particularly when interfacing with legacy systems that require wide-range high-voltage supplies, leading to reliability issues and increased manufacturing costs.
Innovation Solution
The output interface module incorporates a pull-up circuitry coupled with a level shifter that provides multiple turn-on voltage levels to prevent voltage stress on transistors, utilizing drain-extended MOSFETs (De-MOS) that can withstand higher voltages across their drain-gate, drain-source, and drain-bulk nodes, while maintaining a thin-film architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-voltage thin-film transistors are used for cost saving, then manufacturing cost is reduced, but the transistors cannot withstand high-voltage applications (e.g., 10V) without voltage stress
Solution Approach 1:
A level shifter circuit is introduced as an intermediary component between the high-voltage interface and the low-voltage thin-film transistor core logic. The level shifter converts high-voltage signals to low-voltage signals that the thin-film transistors can safely process, thereby protecting the transistors from voltage stress while enabling high-voltage interface compatibility
Solution Approach 2:
The patent changes the voltage parameter of the transistor gate oxide from thin (low-voltage tolerant) to thick (high-voltage tolerant) in specific regions where high-voltage stress occurs. This parameter modification allows the transistor to withstand higher voltages without dielectric breakdown, enabling high-voltage interface support while maintaining cost-effective thin-film fabrication processes
2Reliability
If thick-oxide high-voltage transistors are used to withstand high voltage, then voltage stress resistance is improved, but manufacturing cost increases
Solution Approach 1:
Instead of making all transistors in the IC with thick oxide, the patent applies thick-oxide technology only to specific transistors that are exposed to high-voltage stress (such as those in the level shifter or high-voltage interface circuits). The majority of the IC continues to use cost-effective thin-oxide transistors, thereby achieving high-voltage tolerance where needed while minimizing manufacturing cost increases
3Adaptability or versatility
If low-voltage transistors are used with wide-range high-voltage supply, then adaptability to legacy interfaces is improved, but the transistors suffer from voltage stress and reliability deteriorates
Solution Approach 1:
The level shifter acts as a mediator that enables the low-voltage transistor-based IC to interface with high-voltage legacy systems. It translates high-voltage input signals to appropriate low-voltage levels for the internal transistor logic, and also translates low-voltage output signals to high-voltage levels for the external interface, thereby achieving wide-range voltage adaptability without exposing the transistors to damaging voltage stress
Data Source
AI summary
A wide-voltage range, failsafe output interface module including a low-voltage, drain extended MOSFETs has been proposed to prevent the flow of reverse current during a failsafe operation while ensuring the MOSFETs are not subject to voltage over their voltage tolerance levels, improving reliability of an output interface module without resorting to more costly transistors with thicker films.