Non-Volatile Memory Read Voltage Shift Control by Bit Count Tracking
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Solution Overview
Problem
Existing memory systems face challenges in efficiently managing and controlling non-volatile memory devices, particularly in accurately determining the number of bits stored in memory cell transistors and adjusting read voltages to ensure reliable data retrieval.
Innovation Solution
A memory system and method that includes a memory controller capable of calculating shift amounts for read voltages based on count values of write data and read voltages, utilizing a bit count management table to manage information on cell units, and performing patrol reads to update shift amounts, ensuring accurate data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If read voltage is adjusted without accurate bit count management, then data retrieval speed is maintained, but data retrieval accuracy deteriorates
Solution Approach 1:
The memory chip is divided into multiple cell units, each with its own bit count management table. This segmentation allows independent tracking of bit counts for each cell unit, enabling accurate read voltage adjustment without requiring system-wide complex management. The bit count management table is further divided into tables for different cell units (first cell unit table, second cell unit table, etc.).
Solution Approach 2:
The memory chip autonomously manages its own bit count information through internally stored bit count management tables. The counter circuit automatically counts bits during write operations and stores this information in the bit count management table, eliminating the need for external controller intervention in the bit counting process.
2Measurement precision
If bit count management is performed for all cell units, then data retrieval accuracy is improved, but device complexity increases
Solution Approach 1:
Instead of using a single centralized bit count management table for all cell units, the system segments the management structure into multiple separate bit count management tables, with each table dedicated to a specific cell unit. This segmentation reduces the complexity of each individual table while maintaining comprehensive tracking across all cell units.
3Reliability
If read voltage shift amount is not updated through patrol reads, then operation speed is maintained, but data retrieval reliability deteriorates
Solution Approach 1:
Instead of performing comprehensive patrol reads on all cell units, the system selectively updates read voltage shift amounts only for cell units where necessary. The controller determines which cell units require patrol reads based on current operational conditions, applying partial action to maintain reliability while minimizing time loss.
Data Source
AI summary
According to one embodiment, a memory system includes a memory chip including a plurality of memory cells each of which is capable of storing data corresponding to one of a plurality of states and a memory controller. The memory controller is configured to control a write operation and a read operation performed on the memory cells and calculate a shift amount of a read voltage in the read operation based on at least one of a plurality of first count values of write data corresponding to the plurality of states in the write operation and a second count value corresponding to the read voltage.