EPLI Comparator for Non-Volatile Memory Blank Check Reliability
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Solution Overview
Problem
Blank checking in non-volatile memory devices is unreliable, leading to sectors being incorrectly identified as erased due to power losses or failures during the erase operation, which can result in incomplete erasure and subsequent issues during reading and writing.
Innovation Solution
The implementation of Erase Power Loss Indicator (EPLI) bits and a comparator to generate, store, and compare initial and final EPLI values, ensuring that the erase operation is completed before considering a sector blank checked and trusted, thereby preventing re-erasure and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If blank checking is performed to identify erased sectors, then productivity is improved by avoiding re-erasure, but reliability deteriorates due to power losses or failures during erase operation causing incorrect identification
Solution Approach 1:
The patent applies preliminary action by programming EPLI bits with initial values before the erase operation begins. These bits serve as a pre-established reference that will later be compared against final values to verify complete erasure. This preliminary setup enables reliable blank checking even when power loss occurs during the erase process, as the initial EPLI values provide a baseline for detecting incomplete erasure.
Solution Approach 2:
The patent implements feedback through the comparison of initial and final EPLI bit values after the erase operation. The controller reads both sets of EPLI values and compares them to determine whether erasure was complete. This feedback mechanism provides verification of the erase operation's success, preventing incorrect identification of erased sectors and enabling reliable blank checking.
2Reliability
If iterative verification procedures are implemented to ensure proper erasure, then reliability is improved, but loss of time increases due to repeated operations
Solution Approach 1:
The patent extracts the verification function from the main erase operation by using dedicated EPLI bits that are programmed separately before and after erasure. Instead of verifying each memory cell individually through iterative read operations, the system extracts the verification task into a simple comparison of EPLI bit values. This extraction dramatically reduces verification time while maintaining reliability.
Solution Approach 2:
The patent uses copying by creating a copy of the EPLI values before erasure (initial values) and comparing it with the values after erasure (final values). This copying approach allows verification without re-reading the actual data cells, significantly reducing the time required for iterative verification procedures while ensuring complete erasure.
Data Source
AI summary
A non-volatile memory device comprising a memory cell array including memory cells distributed among a plurality of sectors; a controller operable to program, read, and erase memory cells in said memory array, said controller further operable to generate and store EPLI values for programming a number of EPLI bits in one of said plurality of sectors with said stored EPLI values; and a comparator to compare said stored EPLI values with EPLI values programmed in said EPLI bits.