Memory Bank Repair Using Data Shift and Redundant Bank Swapping
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Solution Overview
Problem
Existing memory devices face issues with redundant bank designs that waste chip area and reduce flexibility due to a large number of unused redundant banks and increased data line skew from lengthy routing, especially in NAND Flash memory devices.
Innovation Solution
Implement a memory device with a smaller number of redundant banks and a flexible, data shift-based repair scheme using multiplexers to couple adjacent banks, allowing data to be shifted between main and redundant banks, reducing redundant bank area and data line skew.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of redundant banks are provided in the memory device, then repair capability is improved, but chip area is wasted and device complexity increases
Solution Approach 1:
The patent implements a universal repair mechanism where a single redundant bank can replace any failed main bank through bank swapping. The redundant bank is designed to be compatible with all main banks, allowing it to assume the identity and function of any failed bank. This multi-functional approach eliminates the need for dedicated redundant banks for each main bank, significantly reducing the total number of redundant banks required while maintaining full repair capability across the memory device.
Solution Approach 2:
The patent employs a bank swapping mechanism where the identity and configuration of a failed main bank are transferred to a redundant bank. The redundant bank effectively 'recovers' the functional characteristics of the failed bank through this identity transfer process. This allows the memory system to discard the failed bank and recover its functionality in the redundant bank, eliminating the need for extensive redundant banking structures.
2Reliability
If many redundant banks are coupled to main banks with lengthy routing, then repair capability is improved, but data line skew increases and manufacturing precision requirements worsen
Solution Approach 1:
The patent extracts the redundant banks from their traditional positions and consolidates them into a single shared redundant bank location. This extraction eliminates the need for lengthy routing connections from multiple main banks to multiple redundant banks. The single shared redundant bank requires minimal routing, significantly reducing data line skew and relaxing manufacturing precision requirements while maintaining the ability to repair any failed main bank.
3Reliability
If a traditional redundant bank design is used, then repair functionality is provided, but flexibility is reduced due to fixed bank identities
Solution Approach 1:
The patent implements dynamic bank identity assignment where the redundant bank can assume the identity of any failed main bank based on which bank actually fails. This dynamic reconfiguration capability provides maximum flexibility, as the system can adapt to any failure pattern. The bank swapping mechanism allows the redundant bank to dynamically take on the role of the failed bank, enabling flexible repair strategies that were not possible with static, pre-assigned redundant banks.
Data Source
AI summary
In certain aspects, a memory device includes an array of memory cells and an input/output (I/O) circuit. The array of memory cells includes N main banks and M redundant banks. Each of N and M is a positive integer, and N is greater than M. The I/O circuit includes a set of write multiplexers (MUXs) respectively coupled to the N main banks and M redundant banks. Each of the N main banks and M redundant banks is coupled to an individual write MUX of the set of write MUXs.