Shared Pump Circuit for NAND Flash Memory Voltage Control
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Solution Overview
Problem
Conventional NAND flash memory requires multiple local pumps for different voltages, leading to increased circuit area and manufacturing costs due to the need for multiple voltage applications during operations like reading, programming, and erasing.
Innovation Solution
A shared pump circuit for generating gate voltages for multiple nMOS transistors reduces the circuit area by consolidating voltage generation, allowing for efficient voltage transfer to word lines while maintaining control over the rising slope of voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple local pumps are provided for different voltages in conventional NAND flash memory, then voltage control for different operations (reading, programming, erasing) is achieved, but circuit area increases and manufacturing costs increase
Solution Approach 1:
The patent merges multiple local pumps into a single shared pump circuit that serves multiple word lines. Instead of having separate pumps for each voltage level (read voltage, program voltage, erase voltage), the invention uses one pump circuit to generate a boosted voltage that is then selectively distributed to different word lines based on operational requirements. This consolidation directly reduces circuit area while preserving voltage control versatility through selective activation and voltage division mechanisms.
Solution Approach 2:
The shared pump circuit is designed to perform multiple functions: it can generate boosted voltages for read operations, program operations, and erase operations. The pump output is connected to multiple word lines (WL0-WL7) and can be selectively activated to serve different operational modes. This multi-functional design eliminates the need for dedicated pumps for each operation, thereby reducing overall circuit area while maintaining full operational capability.
2Adaptability or versatility
If multiple local pumps are provided for different voltages, then appropriate voltage can be selected for each word line operation, but manufacturing costs increase due to increased circuit area
Solution Approach 1:
By combining multiple pump circuits into a single shared pump, the invention reduces the total component count and circuit area. Fewer components mean simpler manufacturing processes, reduced assembly complexity, and lower material costs. The shared pump architecture maintains voltage selection capability through selective connection to different word lines and use of voltage division circuits, thereby preserving functionality while improving ease of manufacture and reducing costs.
3Area of stationary object
If a shared pump circuit is used to reduce circuit area, then manufacturing costs decrease, but control over voltage boosting speed must be carefully managed
Solution Approach 1:
The invention introduces intermediate components between the shared pump and the word lines to manage voltage distribution. These include switch circuits (controlled by control signals) that selectively connect the pump output to specific word lines, and voltage division circuits that create different voltage levels from a single boosted voltage. These intermediary elements add manageable complexity to control while preserving the area-reducing benefit of the shared pump architecture.
Solution Approach 2:
The shared pump circuit incorporates dynamic control mechanisms where the pump's operation is modulated based on real-time operational requirements. Control signals dynamically adjust the pump's output and selectively activate connections to different word lines. This dynamic behavior allows a single pump to adaptively serve multiple functions and voltage requirements, managing control complexity through intelligent, time-varying operation rather than static, redundant hardware.
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
The shared pump circuit reduces the circuit area and manufacturing costs while maintaining efficient voltage control, allowing for effective voltage transfer and operation across multiple word lines.
Implementation Method 1
a pump circuit adapted to boost a first voltage and output a second voltage obtained by the boosting
Data Source
AI summary
A nonvolatile semiconductor memory comprises a memory cell array in which a plurality of memory cell transistors capable of storing data according to a threshold voltage; a row decoder having a plurality of transfer MOS transistors connected at first ends to a plurality of word lines which are respectively connected to control gate electrodes of the plurality of memory cell transistors; and a word line driver which selects supplied voltages and supplies the selected voltages to second ends of the plurality of transfer MOS transistors. The nonvolatile semiconductor memory further comprises a voltage generation circuit which supplies voltages to the word line driver; and a control circuit which controls operation of the row decoder, the word line driver and the voltage generation circuit.