Booster Circuit Timing Control for Nonvolatile Memory
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Solution Overview
Problem
Conventional nonvolatile semiconductor memory devices require additional circuit components like comparators, ROM, and regulators to adjust boost voltage arrival time, leading to increased circuit size and potential reliability issues due to improper electric field application during erase and write operations.
Innovation Solution
A booster circuit comprising a booster unit, oscillator circuit, timing generator circuit, and current load circuit, where the current load circuit controls the driving force of the booster unit using timing signals to achieve appropriate boost voltage arrival time without increasing circuit area, by regulating the current load applied to the booster unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the amplitude of boosting clock pulses is increased to enhance the driving force of the booster circuit, then the boost voltage arrival time is shortened, but this causes an increase in the time for which an intense electric field is applied, which accelerates the reliability degradation of the memory cells
Solution Approach 1:
The patent applies dynamics by making the driving force of the booster circuit adjustable rather than fixed. The control system dynamically changes the amplitude of boosting clock pulses based on detected boost voltage arrival time, allowing optimization between speed and reliability. When arrival time is too short, the system reduces clock pulse amplitude to extend the time, preventing reliability degradation while maintaining acceptable boost speed.
Solution Approach 2:
The patent implements feedback control by detecting the actual boost voltage arrival time and using this information to adjust the driving force of the booster circuit. The control system compares the detected arrival time with target values and automatically adjusts the clock pulse amplitude accordingly, creating a closed-loop system that optimizes both boost speed and memory cell reliability.
2Reliability
If the amplitude of boosting clock pulses is decreased to extend the boost voltage arrival time, then the reliability degradation of memory cells is reduced, but this causes a decrease in the time for which the electric field strength required for rewriting is applied to the memory cells, which leads to insufficient rewriting
Solution Approach 1:
The system dynamically adjusts the clock pulse amplitude based on real-time detection of boost voltage arrival time. When the arrival time is detected to be too long, the control system increases the amplitude to shorten the time, ensuring sufficient electric field application duration for effective rewriting while preventing reliability degradation from excessively long times.
Solution Approach 2:
The feedback mechanism detects when boost voltage arrival time is too long and automatically increases the driving force by increasing clock pulse amplitude. This closed-loop control ensures the electric field application time remains within the optimal range for effective rewriting, preventing insufficient rewriting while avoiding excessive time that would degrade reliability.
3Measurement precision
If additional circuit components like comparators, ROM, and regulators are added to adjust boost voltage arrival time, then the boost voltage arrival time control is improved, but the circuit size increases
Solution Approach 1:
The patent achieves multi-functionality by using existing circuit components for multiple purposes. The oscillator circuit that generates clock pulses is also used to control the driving force by adjusting pulse amplitude. The control system utilizes existing timing and detection circuits rather than adding dedicated components, allowing precise boost voltage arrival time control without increasing circuit area.
Solution Approach 2:
The system employs self-service by using its own existing resources for control. The booster circuit's internal oscillation and timing mechanisms are leveraged to detect and adjust boost voltage arrival time. The control system uses the oscillator's own characteristics and existing circuit elements rather than requiring external dedicated control components, achieving precise control without area expansion.
Data Source
AI summary
A nonvolatile semiconductor memory device, having a booster circuit capable of performing a boost operation with appropriate boost voltage arrival time without increasing the circuit size. The nonvolatile semiconductor memory device includes a timing generator circuit and a current load circuit which applies a current load to an output of a booster unit according to a signal from the timing generator circuit, thereby achieving an appropriate boost voltage arrival time by using the current load circuit in concert with the operation of erasing or writing on memory cells.