Level-Aware Bias Voltage Generator for Reliable Level Shifting
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Solution Overview
Problem
Existing level shifters in non-volatile memory systems have a narrow voltage operating range and fail to function reliably during voltage ramp-up periods, leading to potential mis-programming of memory cells.
Innovation Solution
A level-aware bias voltage generator that includes a voltage divider and level shifter architecture with cascoded transistors, using cascoded bias voltages to maintain stable operation across varying power supply voltages, ensuring reliable control of transistors throughout the voltage ramp-up period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing level shifters are used to provide high programming voltage, then the voltage can be generated, but the voltage operating range is narrow and reliability is poor during voltage ramp-up period
Solution Approach 1:
The bias voltage generator dynamically adjusts bias voltages based on the power supply voltage level. During voltage ramp-up, the generator detects the rising voltage and provides appropriate bias voltages to keep transistors in their linear region throughout the entire voltage range, not just at steady-state. This dynamic adaptation resolves the contradiction by making the level shifter reliable across the full voltage operating range rather than only at fixed voltage levels.
Solution Approach 2:
The invention changes the bias voltage parameters dynamically according to the power supply voltage. By adjusting the bias voltages for transistors based on the instantaneous power supply voltage level, the system maintains optimal transistor operation across varying voltage conditions. This parameter adjustment enables the level shifter to operate reliably from low voltage during ramp-up to high voltage during steady-state operation.
2Productivity
If high programming voltage is applied during voltage ramp-up, then programming operation can be performed, but transistor operation becomes unstable and mis-programming may occur
Solution Approach 1:
The bias voltage generator performs preliminary action by establishing appropriate bias voltages before and during the voltage ramp-up period. By proactively adjusting the bias voltages in anticipation of the voltage changes, the system ensures transistors remain in their linear region throughout the ramp-up process. This preliminary biasing prevents instability and mis-programming that would otherwise occur during voltage transitions.
Solution Approach 2:
The system implements feedback by monitoring the power supply voltage level and using this information to adjust the bias voltages accordingly. The bias voltage generator responds to voltage changes in real-time, creating a closed-loop control system that maintains transistor stability. This feedback mechanism ensures that programming operations can proceed reliably even during voltage ramp-up by continuously adapting the bias conditions.
Data Source
AI summary
The present disclosure provides a semiconductor device and a bias voltage generator. The semiconductor device includes a voltage divider, a voltage selection circuit, and a level shifter. The voltage divider is configured to divide a power supply voltage to generate a first bias voltage. The voltage selection circuit is configured to select between the first bias voltage and a reference voltage to output a second bias voltage. The level shifter is configured to adjust a voltage level of the power supply voltage using the first bias voltage and the second bias voltage.