Flash Memory Bad Block Remapping Using Existing Address Signals
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Solution Overview
Problem
Flash memory devices face issues with defective memory cells forming bad blocks, leading to device failure, and existing bad block management methods require separate bussing of redundant block address signals, increasing chip size.
Innovation Solution
A non-volatile memory device with a bad block remapping function that uses existing block address signals to select remapping blocks from main cell blocks, eliminating the need for separate bussing of remapping block address signals by employing a remapping block mapping controlling unit to generate and select addresses for replacing bad blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate bussing of remapping block address signals is used to select redundant blocks, then bad block remapping function is achieved, but chip size increases
Solution Approach 1:
The patent makes the existing block address signals serve dual purposes: both addressing main cell blocks and selecting remapping blocks. The row decoder unit decodes row address signals to generate block address signals that can address both main cell blocks and remapping blocks, eliminating the need for separate bussing of remapping block address signals.
Solution Approach 2:
The patent merges the addressing function for main cell blocks and remapping blocks into a single block address signal bus. The remapping block mapping controlling unit controls the row decoder to generate appropriate block address signals based on whether the target is a main cell block or a remapping block, combining what were previously separate signal paths.
2Area of stationary object
If existing block address signals are used to select remapping blocks, then chip size is reduced, but address signal routing complexity increases
Solution Approach 1:
The remapping block mapping controlling unit acts as an intermediary between the external block address input and the row decoder. It compares the external block address with stored bad block addresses, determines whether remapping is needed, and controls the row decoder to generate the appropriate block address signals for either main cell blocks or remapping blocks.
Solution Approach 2:
The patent pre-stores bad block addresses in the remapping block mapping controlling unit during manufacturing or initial operation. This preliminary identification and storage of bad block addresses enables the system to quickly determine during operation whether remapping is needed without complex real-time analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces chip size by eliminating the need for separate bussing of remapping block address signals, effectively managing bad blocks within the existing address framework, thereby enhancing the reliability and efficiency of flash memory devices.
Implementation Method 1
a row decoder unit decoding a row address signal to generate block address signals addressing the main cell blocks
Implementation Method 2
a remapping block mapping controlling unit configured to compare an external block address input by an external source and a bad block address stored in a chip, generate a bad block flag signal, generate a remapping block address for selecting the remapping blocks
Data Source
AI summary
A non-volatile memory device and a bad block remapping method use some of main blocks as remapping blocks to replace a bad block in a main cell block and selects remapping blocks using existing block address signals. Thus, separate bussing of remapping block address signals is not needed. The bad block remapping includes comparing an external block address input from an external source to a stored bad block address, generating a bad block flag signal when the external block address is identical to the stored bad block address, generating a remapping block address selecting the remapping blocks in response to a remapping address corresponding to the bad block address, selecting one of the external block address and the remapping block address in response to the bad block flag signal to create a selected address, and outputting a row address signal in accordance with the selected address.