Non-Volatile Memory Cell State Detection via Complementary Pairs
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Solution Overview
Problem
Existing Non-Volatile Memory (NVM) systems face issues with accurately reading data from NVM cells, particularly in determining whether a cell group is in an erased or programmed state, leading to potential corruption of information during user read operations, especially when dealing with complementary cell pairs.
Innovation Solution
A method and system that utilize complementary cell pairs, sense amplifiers, and a controller to determine the state of NVM cells by counting binary values and comparing them to a programmable threshold, ensuring accurate output of either a predetermined binary state or the result of a complementary read, thereby preventing data corruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single read command is used to access NVM cells, then read operation speed is improved, but data corruption may occur when determining the state of cell groups
Solution Approach 1:
The patent applies preliminary action by performing a reference read sequence before the actual read operation to determine whether the cell group is in an erased or programmed state. This preliminary determination allows the system to prepare appropriate reference levels and read voltages in advance, ensuring accurate data retrieval in a single read command without corruption.
Solution Approach 2:
The patent uses an intermediary approach by introducing a reference read sequence that acts as a mediator between the read command and the data output. This reference sequence provides intermediate information about the cell group state, which is then used to adjust the main read operation parameters, preventing data corruption while maintaining speed.
2Reliability
If complementary cell pairs are used to store data, then data redundancy and reliability are improved, but the complexity of determining cell state increases
Solution Approach 1:
The patent applies segmentation by dividing the cell group into complementary cell pairs (first cell and second cell) with distinct roles. The first cell stores the actual data while the second cell serves as a complementary reference. This segmentation simplifies the state determination process by allowing the system to compare known complementary states rather than analyzing the entire cell group uniformly.
Solution Approach 2:
The patent uses homogeneity by ensuring that complementary cell pairs maintain consistent and predictable state relationships. When one cell is in a programmed state, its complement is in an erased state, and vice versa. This homogeneous complementary relationship simplifies the read logic and state determination complexity.
3Measurement precision
If threshold comparison is used to determine cell state, then measurement precision is improved, but the system requires programmable thresholds that increase device complexity
Solution Approach 1:
The patent applies self-service by having the system automatically determine and set appropriate threshold values based on the reference read sequence results. The controller autonomously adjusts the read threshold according to the determined cell group state (erased or programmed) without requiring external programming or manual calibration, thereby maintaining measurement precision while reducing the operational complexity of threshold management.
Data Source
AI summary
Disclosed is a method for responding to a single user read command of a complementary cell array including one or more complementary cell pairs, the method including: determining if a first group of cells out of a data word is in an erased state or in a programmed state, and outputting a data word so that (a) if the first group of cells is determined to be erased a logical “one” is output for each bit of the data word and (b) if the first group of cells is determined to be programmed the result of a complementary read is output for each bit of the data word.