Column Redundancy Using Data Latches in Solid-State Memories
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Solution Overview
Problem
Conventional column redundancy schemes in non-volatile memory devices are slow and inefficient due to the need for multiple stages of logic to replace defective columns, which limits data input/output rates and inefficient remapping of defective columns, especially when redundant data is localized at the latches of the redundant columns.
Innovation Solution
The proposed solution relocates redundant data from redundant data latches to more accessible locations, such as data latches of defective columns, allowing for virtual defect-free operation by using only the user portion's addressing scheme, eliminating the need to switch to redundant data latches during defective column encounters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional column redundancy schemes are used to replace defective columns, then defect management is achieved, but data input/output rates are limited due to multiple stages of logic required for remapping
Solution Approach 1:
The patent pre-loads redundant data into data latches before it is needed during read operations. When a defective column is detected, the corresponding redundant data is already available in the latches, eliminating the need for complex remapping logic during the actual data access operation. This preliminary preparation resolves the contradiction by maintaining high data I/O rates while ensuring defect management capability.
2Device complexity
If redundant data is localized at the latches of redundant columns, then storage organization is simplified, but access efficiency decreases requiring switching to redundant data latches during defective column encounters
Solution Approach 1:
The patent makes the data latches universal by enabling them to store both user data and redundant data. The same data latches that normally hold user data are also capable of holding redundant data when needed, eliminating the requirement for separate redundant data latches. This multi-functionality resolves the contradiction by maintaining simple storage organization while improving access efficiency, as no switching between different latch sets is required.
Data Source
AI summary
A memory has defective locations in its user portion replaceable by redundant locations in a redundant portion. Data latches in the user and redundant portions allow data sensed from or to be written to a memory to be exchanged with a data bus. A defective location latching redundancy scheme assumes the column circuits including data latches for defective columns to be still useable. The data latches for the defective columns are used to buffer corresponding redundant data that are normally accessible from their data latches in the redundant portion. In this way both the user and redundant data are available from the user data latches, and streaming data into or out of the data bus is simplified and performance improved.