Cross-Coupled Level Shifter Circuit for Stable Multi-Voltage Conversion
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Solution Overview
Problem
Current CMOS level shifters are not stable and require additional power and surface area to compensate for voltage and current variations, introducing complexity and instability, which affects the performance of input/output circuits in modern microprocessors.
Innovation Solution
A level shifter circuit design that splits a PMOS cross-coupled latch into two parts, using a first weak transistor and a first strong transistor, and a second weak transistor and a second strong transistor, with cross-coupling and toggling using a thin-oxide inverter to manage state transitions and voltage conversion between multi-voltage domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current CMOS level shifters are used for voltage conversion, then voltage level conversion is achieved, but stability deteriorates and additional power and surface area are required
Solution Approach 1:
The level shifter circuit is segmented into two independent PMOS cross-coupled latches (first and second latches). Each latch operates independently to handle different voltage domains, eliminating the need for complex compensation circuits and reducing power consumption while improving stability.
Solution Approach 2:
A weak PMOS transistor is introduced as an intermediary element between the two latches to control the timing of state transitions. This weak transistor acts as a mediator that enables controlled signal propagation from the first latch to the second latch, ensuring stable operation during voltage level transitions.
2Reliability
If current CMOS level shifters are used for voltage conversion, then voltage level conversion is achieved, but device complexity increases
Solution Approach 1:
The level shifter is divided into two simple PMOS cross-coupled latches with a weak PMOS transistor, replacing complex differential cascade voltage switch circuits or Wilson current mirror configurations. This segmentation simplifies the overall circuit topology while maintaining stability.
Solution Approach 2:
Different PMOS transistors are designed with different strength characteristics (strong vs. weak) to perform specific functions. The strong PMOS transistors provide stable latching, while the weak PMOS transistor controls transition timing, creating local functional differentiation that simplifies the overall design.
3Reliability
If additional compensation circuits are added to current CMOS level shifters, then voltage and current variations are compensated, but power consumption and surface area increase
Solution Approach 1:
The circuit uses two compact PMOS cross-coupled latches instead of large compensation circuits. Each latch is a minimal structure that provides inherent stability, reducing the total surface area required while maintaining voltage and current stability.
Solution Approach 2:
The PMOS cross-coupled latches provide self-compensation for voltage and current variations through their inherent positive feedback mechanism. The strong PMOS transistors automatically adjust to maintain stable operation without requiring external compensation circuits.
Data Source
AI summary
The present disclosure relates to an apparatus including level shifter circuitry configured to convert a voltage between one or more multi-voltage domains. The apparatus may include an integrated circuit having a cross-coupled latch including a first weak transistor cross-coupled with a second weak transistor. The integrated circuit may further include a first strong transistor in parallel with the first weak transistor and a second strong transistor in parallel with the second weak transistor. The integrated circuit may further include an inverter configured to toggle at least one of the first weak transistor and the second weak transistor.