MRAM Built-In Self-Test Trim Search With Address Skipping
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Solution Overview
Problem
The challenge of setting reference resistance in MRAM devices is difficult due to small resistance separation between high and low resistive states, and existing memory built-in self-test systems face long search times, making them impractical for larger implementations.
Innovation Solution
An automated reference trim search process with address skipping is implemented, using a memory built-in self-test system that determines boundary values for data types '0' and '1' through a binary search sequence, adjusting the reference trim based on failure detection and feedback, and applying this process to multiple memory banks efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If traditional memory built-in self-test systems are used to perform reference trim searching, then the reference trim can be automatically set, but the search time becomes excessively long making it impractical for larger MRAM implementations
Solution Approach 1:
The patent divides the memory device into multiple memory banks and performs reference trim searching on a per-bank basis rather than testing the entire memory device at once. This segmentation allows the trim search process to be completed more quickly by processing smaller subsets of memory cells in parallel or sequentially, reducing the overall search time while maintaining automatic operation.
Solution Approach 2:
The patent applies partial action by performing reference trim searching on only one memory bank at a time rather than all banks simultaneously. The process determines boundary values for data types '0' and '1' for a single bank, then repeats for other banks. This partial approach reduces the complexity and time required for each testing iteration while still achieving complete coverage across all banks.
2Measurement precision
If extensive testing over different environmental conditions is performed to identify reference trims, then accurate reference trim values can be determined, but the testing becomes costly and impractical for larger MRAM implementations
Solution Approach 1:
The patent implements a self-service approach where the memory device performs its own reference trim searching and setting automatically through built-in self-test circuitry. The system determines boundary values and sets reference trims without requiring external testing equipment or manual intervention, thereby maintaining accuracy while dramatically improving testing efficiency and reducing costs.
Solution Approach 2:
The patent changes the testing approach by using parameter-based boundary value determination instead of extensive environmental condition testing. The system determines boundary values for data types '0' and '1' based on failure conditions and uses these parameters to set reference trims, achieving accurate results through parameter optimization rather than environmental stress testing.
3Reliability
If reference trim searching is performed on all memory banks, then complete coverage is achieved, but the search time increases significantly
Solution Approach 1:
The patent segments the memory device into multiple banks and performs reference trim searching on individual banks rather than testing all banks simultaneously. This segmentation maintains complete testing coverage by ensuring each bank is tested, while reducing search time by processing smaller subsets of memory cells and potentially parallelizing the process across multiple banks.
Data Source
AI summary
An address-skipping trim search performed by a memory built-in self-test system comprises: perform memory read operations on one memory bank to determine whether it fails to correctly sense values of stored data based on a reference trim value for a previous memory bank; if the present memory bank fails, perform memory read operations to search for a new reference trim value for the present memory bank; or otherwise, treat the present reference trim value as the one for the present memory bank and proceed to testing a next memory bank. The range for searching for the new reference trim value can be limited by the present reference trim value.