Sense Amplifier Circuit for NAND Flash Memory
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Solution Overview
Problem
NAND-type flash memory devices face limitations in data transmission speed due to lower cell current compared to NOR-type flash memories, making it difficult to achieve high-speed data sensing, and increasing cell size to enhance current would compromise the compact nature of NAND-type flash memory cells.
Innovation Solution
A semiconductor memory device with a memory cell array and a sense amplifier circuit that detects cell current differences between information cells and reference cells, allowing for multi-value data storage and improved data sensing by utilizing multiple physical quantity levels and a reference cell to enhance data reading efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If cell size is increased to enhance cell current, then data sensing speed is improved, but cell area increases and compactness is lost
Solution Approach 1:
A reference cell is introduced as an intermediary element to enable differential sensing. The reference cell stores a reference physical quantity level that serves as a comparison基准 for the information cell's data level, allowing accurate data sensing without requiring larger cell dimensions. This mediator approach resolves the contradiction by providing a reference framework that enhances sensing capability while maintaining compact cell size.
Solution Approach 2:
The invention utilizes multiple physical quantity levels (M≥2) stored in the memory cell, transforming the sensing approach from binary to multi-level detection. By changing the parameter of physical quantity levels and using differential comparison between information and reference cells, the system achieves high-speed sensing without increasing cell area, as the speed improvement comes from the sensing methodology rather than cell size.
2Quantity of substance
If NAND-type flash memory is used to achieve high capacity, then storage density is improved, but data transmission speed decreases due to lower cell current
Solution Approach 1:
The reference cell acts as a mediator that enables high-speed data transmission in NAND-type flash memory by providing a differential sensing mechanism. This approach allows the system to overcome the inherently lower cell current of NAND cells while maintaining high storage density, as the speed enhancement comes from the comparative sensing method rather than increasing individual cell current.
Solution Approach 2:
By implementing multi-value data storage using M physical quantity levels and differential sensing against a reference cell, the invention transforms the performance characteristics of NAND flash memory. This parameter change in the sensing methodology enables high-speed data transmission while preserving the high storage capacity advantage of NAND architecture.
3Quantity of substance
If multi-value data storage is implemented, then storage capacity is improved, but read time increases due to multiple read operations required
Solution Approach 1:
The reference cell is pre-configured with a reference physical quantity level before data reading operations. This preliminary setup enables direct differential comparison during the read operation, eliminating the need for multiple sequential read operations that would otherwise be required to interpret multi-level data. The pre-established reference framework reduces read time while maintaining multi-value storage capacity.
Solution Approach 2:
The reference cell serves as an intermediary that enables single-step differential sensing of multi-level data. By comparing the information cell's physical quantity level directly against the reference cell's predetermined level, the system can determine stored data in one operation rather than requiring multiple reads, thus reducing read time while preserving high storage capacity.
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 solution enables faster data sensing and storage of multiple data values in a compact form, bridging the speed gap with NOR-type flash memories while maintaining the small cell area advantage of NAND-type flash memories.
Implementation Method 1
the sense amplifier circuit detects a cell current difference between the information cell and the reference cell selected simultaneously in the memory cell array to sense data defined by the M physical quantity levels of the information cell
Data Source
AI summary
A semiconductor memory device includes: a memory cell array with electrically rewritable and non-volatile memory cells arranged therein; and a sense amplifier circuit configured to read out data of the memory cell array, wherein a plurality of information cells, in each of which one of M(M≧2) physical quantity levels is written, and at least one reference cell, in which a reference physical quantity level is written, are defined in the memory cell array, and the sense amplifier circuit detects a cell current difference between the information cell and the reference cell selected simultaneously in the memory cell array to sense data defined by the M physical quantity levels of the information cell.