Charge Pump Stage Isolation for Multilevel Flash Memory
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Solution Overview
Problem
Conventional charge pumps in multilevel flash memory systems suffer from inadequate isolation between pump stages, leading to short circuits and instability in voltage signal maintenance, especially during low voltage operations.
Innovation Solution
The charge pump system incorporates multiple pump stages with discharge circuitry and precharge circuitry, including self-discharge and self-precharging features, to ensure orderly charging and discharging, prevent cascaded short circuits, and maintain stable voltage levels by using native NMOS transistors and capacitors, along with anti-parallel configurations and buffering mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional charge pumps are used with multiple pump stages, then voltage multiplication is achieved, but isolation between pump stages is insufficient leading to short circuits and instability
Solution Approach 1:
The charge pump is divided into multiple independently isolated pump stages, where each stage has its own flying capacitors and switching network. This segmentation prevents short circuits between stages while maintaining voltage multiplication capability across the entire system.
Solution Approach 2:
Isolation circuitry is introduced between adjacent pump stages to prevent direct electrical connection. This intermediary structure allows voltage to be multiplied across stages while blocking harmful interactions and short circuits that would otherwise occur between neighboring stages.
2Loss of energy
If charge pump stages operate at low voltage conditions, then power consumption is reduced, but orderly charging and discharging becomes difficult to maintain
Solution Approach 1:
The charge pump incorporates self-precharging circuitry that automatically prepares flying capacitors before each pumping cycle. This self-service mechanism ensures orderly charging and discharging operations are maintained even at low voltage conditions where external control might be insufficient.
Solution Approach 2:
Precharge circuitry is implemented to prepare the flying capacitors in advance before the main pumping operation begins. This preliminary action ensures that capacitors are properly charged and ready for the next cycle, maintaining operational stability during low voltage conditions.
3Device complexity
If pump stages are closely coupled to reduce device complexity, then manufacturing is simplified, but cascaded short circuits can occur among stages
Solution Approach 1:
The harmful coupling effects between pump stages are extracted and removed by introducing isolation circuitry. This separation eliminates the pathway for cascaded short circuits while preserving the beneficial close coupling for voltage multiplication, effectively removing the harmful interaction without sacrificing system integration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the stability and efficiency of charge pumping, allowing for reliable generation and maintenance of high voltage signals even when adjacent stages discharge, thereby preventing short circuits and ensuring consistent output.
Implementation Method 1
Each pump stage may include a plurality of capacitors
Implementation Method 2
using native NMOS transistors and capacitors
Data Source
AI summary
Digital multilevel memory systems and methods include a charge pump for generating regulated high voltages for various memory operations. The charge pump may include a plurality of pump stages. Aspects of exemplary systems may include charge pumps that performs orderly charging and discharging at low voltage operation conditions. Additional aspects may include features that enable state by state pumping, for example, circuitry that avoids cascaded short circuits among pump stages. Each pump stage may also include circuitry that discharges its nodes, such as via self-discharge through associated pump interconnection(s). Further aspects may also include features that: assist power-up in the various pump stages, double voltage, shift high voltage levels, provide anti-parallel circuit configurations, and/or enable buffering or precharging features, such as self-buffering and self-precharging circuitry.