Memory Reference Cell Multiplexer for Read Endurance
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Solution Overview
Problem
Memory devices face challenges in read operations due to small read sensing windows and errors caused by the slight differences in reference cells, leading to reliability and endurance issues, as each column of the memory array has a reference cell that is accessed frequently, resulting in stress and potential data flipping.
Innovation Solution
A memory device structure that utilizes a multiplexer to sequentially and repeatedly select reference cells across columns or rows, maintaining equality by averaging values, thereby reducing stress on individual reference cells and ensuring accurate data reading through a controller-generated column or row control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If each column of memory array has one reference cell for read operation, then the read operation can be performed with simple structure, but the reference cell encounters read endurance and reliability issues due to large number of access times
Solution Approach 1:
The invention divides the single reference cell into multiple reference cells (first reference cell and second reference cell) within the same column. This segmentation allows the sense amplifier to selectively access different reference cells, distributing the access load and reducing wear on individual reference cells, thereby improving read endurance while maintaining structural simplicity.
2Measurement precision
If reference cell is accessed frequently for read operation, then accurate data reading can be achieved, but the reference cell experiences stress and potential data flipping
Solution Approach 1:
The invention implements periodic switching between the first reference cell and the second reference cell during read operations. The controller alternates the selection of reference cells in a periodic manner, which distributes the access stress over time and prevents any single reference cell from being over-stressed, thereby maintaining data reading accuracy while reducing reference cell degradation.
3Reliability
If multiple reference cells are used to reduce stress, then read endurance is improved, but the device complexity increases with multiplexer and control signals
Solution Approach 1:
The invention introduces a multiplexer as an intermediary component that selectively connects either the first reference cell or the second reference cell to the sense amplifier. This intermediary device manages the complexity of switching between multiple reference cells while maintaining a relatively simple overall structure, allowing the system to benefit from multiple reference cells without proportionally increasing device complexity.
Data Source
AI summary
A memory device for sensing memory cell in a memory array includes at least one first memory cell, a first sensing amplifier, a first multiplexer circuit, a plurality of first reference cells, and a controller. The first sensing amplifier is coupled to the at least one first memory cell. An output terminal of the first multiplexer circuit is coupled to the reference terminal of the first sensing amplifier. Each of the first reference cells is coupled to each input node of the first multiplexer circuit. The controller is coupled to a control terminal of the first multiplexer circuit. The first sensing amplifier comprises an output terminal and a reference terminal. The controller controls the first multiplexer circuit to select one of the first reference cells as a selected reference cell to couple to the reference terminal of the first sensing amplifier when each read operation to the at least one first memory cell is performed.