Reference-Voltage Level Shifter for Full-Range PVT-Stable Output
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Solution Overview
Problem
Conventional level shifters in system-on-chip (SoC) devices are limited by their inability to generate output voltages that reach the minimum and maximum levels of other voltage domains due to voltage protection constraints, leading to inefficiencies and increased size and reduced speed due to the need for large transistors to mitigate PVT variations.
Innovation Solution
A level shifter design comprising a pull-down circuit, a pull-up circuit, a protection circuit, and an output generator, which uses reference and bias voltages to generate output voltages that can reach the desired voltage levels without relying on large transistors, thereby reducing size and increasing speed by minimizing the impact of PVT variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large-sized transistors are implemented in the voltage protection circuit to reduce PVT variations, then the output voltages become stable, but the size of the level shifter increases and the speed of operation degrades
Solution Approach 1:
The level shifter is divided into distinct functional modules: voltage protection circuit, pull-up circuit, pull-down circuit, and output generator. Each module performs a specific function, allowing the use of smaller transistors in the output stage while maintaining overall stability through the coordinated action of specialized sub-circuits.
Solution Approach 2:
The voltage protection circuit acts as an intermediary between the input voltage domain and the output voltage domain. It generates reference voltages that mediate the voltage translation process, enabling the output stage to use smaller transistors while still achieving stable output voltages through the protective and reference functionality provided by the intermediate circuit.
2Reliability
If large-sized transistors are implemented in the voltage protection circuit to reduce PVT variations, then the output voltages become stable, but the speed of operation degrades
Solution Approach 1:
By segmenting the level shifter into specialized modules, the voltage protection circuit can focus on generating stable reference voltages without the burden of driving large output currents. The output generator module handles the speed-critical signal transmission with smaller, faster transistors, while the protection circuit ensures stability through its reference voltage generation functionality.
Solution Approach 2:
The voltage protection circuit serves as an intermediary that prepares stable reference voltages before they reach the output stage. This intermediary function allows the output transistors to be smaller and faster, as they only need to switch based on well-defined reference levels rather than directly handling the full voltage translation burden.
3Reliability
If voltage protection circuit is added to protect transistors from high voltages, then transistor damage is prevented, but the output voltages cannot reach minimum and maximum voltage levels of the other voltage domain
Solution Approach 1:
The voltage protection circuit generates reference voltages that act as intermediaries between the input and output voltage domains. These reference voltages enable the output transistors to safely operate at lower voltage levels while still producing full-range output voltages, as the protection circuit mediates the voltage translation through controlled reference level generation.
Solution Approach 2:
The voltage protection circuit changes the voltage parameters by generating reference voltages at specific levels that enable the output stage to achieve the full voltage range. By carefully controlling the reference voltage levels, the circuit allows output transistors to operate safely at reduced voltage stress while maintaining the ability to produce minimum and maximum output voltage levels.
Data Source
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AI summary
A level shifter includes a pull-down circuit, a pull-up circuit, a protection circuit, and an output generator. The pull-down circuit is configured to receive input voltages, and generate bias voltages. The input voltages are associated with a voltage domain. The pull-up circuit is configured to receive a supply voltage and generate control voltages. The protection circuit is configured to receive reference voltages, and control the generation of the bias voltages and the control voltages. The output generator is configured to receive at least one of the reference voltages, and at least one of the bias voltages and the control voltages, and generate output voltages that are able to reach minimum and maximum voltage levels of another voltage domain. Further, the output voltages remain unaffected by variations in process, voltage, and temperature.