Bias-Controlled Voltage Level Shifter for SOA-Safe Negative Voltages
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Solution Overview
Problem
Existing voltage level shifters face challenges in ensuring that all transistors operate within safe operation areas (SOA) when dealing with varying voltage conditions, especially when a negative reference voltage is applied.
Innovation Solution
The proposed voltage level shifter incorporates a main level shifter and two bias level shifters to generate bias voltages that ensure all transistors within the main level shifter operate within SOA regulations, even under different operational modes such as erase and non-erase modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a negative reference voltage is applied to the level shifter to expand voltage range, then adaptability is improved, but transistors may violate SOA regulations
Solution Approach 1:
The patent introduces bias level shifters as intermediary components that generate intermediate voltage levels (e.g., -3V, -6V) between the negative reference voltage and ground. These intermediary voltage levels are used to bias the gates of transistors in the main level shifter, ensuring that voltage differences across transistor terminals remain within SOA limits while still enabling the level shifter to operate across a wide voltage range. The bias level shifters act as mediators that reconcile the conflict between wide voltage range operation and SOA compliance.
2Reliability
If bias level shifters are added to ensure SOA compliance, then reliability is improved, but device complexity increases
Solution Approach 1:
The bias level shifters are designed to perform multiple functions: they generate bias voltages for different groups of transistors, provide voltage level shifting capability, and ensure SOA compliance across various operating conditions. By making the bias level shifters multi-functional, the patent reduces the need for additional separate components, thereby limiting the increase in device complexity while maintaining high reliability.
3Reliability
If all transistors are biased to meet SOA regulations, then reliability is improved, but voltage shifting capability may be limited
Solution Approach 1:
The patent employs dynamic biasing where the bias voltages generated by the bias level shifters are adjusted based on the operating mode and voltage levels. The bias voltages are not fixed but adapt to different conditions, allowing the main level shifter to maintain SOA compliance while achieving wide voltage shifting capability. This dynamic adjustment enables the system to optimize both reliability and adaptability simultaneously.
Data Source
AI summary
A voltage level shifter is provided. The voltage level shifter includes a main level shifter, a first bias level shifter and a second bias level shifter. The main level shifter includes a first N-type transistor and a second N-type transistor cross-coupled to each other, a third N-type transistor and a fourth N-type transistor controlled by a first bias voltage, a fifth N-type transistor and a sixth N-type transistor respectively controlled by a second bias voltage and a third bias voltage, and a first P-type transistor and a second P-type transistor configured to respectively receive an input signal and an inverted input signal which have opposite voltage values. The first bias level shifter generates the first bias voltage according to an enable signal. The second bias level shifter generates the second bias voltage and the third bias voltage according to the first bias voltage and the input signal.