Non-Volatile Memory Encoding for Unequal State Retention
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Solution Overview
Problem
Non-volatile memory devices face data retention issues due to different retention failure rates in the two states of memory elements, affecting data reliability, particularly when the number of binary ones and zeros in stored data differs.
Innovation Solution
Implementing a reliability indicator to determine the majority or minority bit value based on the data distribution, using a write circuit and read circuit to store and retrieve data in more or less preferred states of bit cells, and employing a sense amplifier to manage data reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is stored in non-volatile memory elements with two states, then storage capacity is achieved, but data reliability deteriorates due to different retention failure rates in the two states
Solution Approach 1:
The patent changes the parameter of bit storage by introducing a reliability indicator that determines whether to store bits in the more preferred state or less preferred state based on the data distribution (majority/minority bits). This parameter change allows dynamic adaptation to different data patterns, optimizing retention performance.
Solution Approach 2:
The patent performs preliminary analysis of data distribution before storage to identify majority and minority bits. This preliminary action enables the system to pre-determine the optimal storage state for each bit, preventing retention errors before they occur rather than correcting them after retrieval.
2Reliability
If majority bits are stored in more preferred states and minority bits in less preferred states, then retention errors are minimized, but device complexity increases due to additional circuits for determining and managing reliability indicators
Solution Approach 1:
The reliability indicator serves multiple functions: it guides the write circuit in selecting optimal storage states, enables the read circuit to retrieve data with corrected polarity, and provides information for majority logic decoding. This multi-functionality reduces the need for separate dedicated circuits for each function.
Solution Approach 2:
The reliability indicator acts as an intermediary between the data and the storage/read operations. It mediates the interaction by providing guidance information that simplifies the decision-making process in both write and read circuits, reducing their complexity while improving overall system reliability.
Data Source
AI summary
A method includes reading a reliability indicator associated with data stored in bit cells. The method also includes reading a stored bit in a bit cell through a sense amplifier and through either a first read path or a second read path selected based on the reliability indicator. The sense amplifier is configured to generate a sensed bit from the stored bit. The first read path is configured to generate a first output bit from the sensed bit when the first read path is selected, and the second read path is configured to generate a second output bit from the sensed bit when the second read path is selected. The first output bit is configured to be a bitwise complement of the second output bit.