Bad column handling in flash memory
First Claim
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1. A multi-plane flash memory array comprising:
- a first plane of flash memory cells comprising first non-redundant columns and first redundant columns, the first non-redundant columns having first bad columns, wherein a number of the first bad columns is less than or equal to a number of the first redundant columns, and wherein each of the first redundant columns stores replacement data for one of the first bad columns; and
a second plane of flash memory cells comprising second non-redundant columns and second redundant columns, the second non-redundant columns having second bad columns, wherein a number of the second bad columns is greater than a number of the second redundant columns, and wherein at least a portion of the second redundant columns stores Error Correction Code (ECC) encoded data and a remaining portion of the second redundant columns stores replacement data for a portion of the second bad columns.
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Abstract
In a flash memory, redundant columns are used alternatively as replacement columns for replacing bad columns or to provide additional redundancy for ECC encoding. Locations of bad columns are indicated to a soft-input ECC decoder so that data bits from bad columns are treated as having a lower reliability than data bits from other columns.
28 Citations
8 Claims
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1. A multi-plane flash memory array comprising:
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a first plane of flash memory cells comprising first non-redundant columns and first redundant columns, the first non-redundant columns having first bad columns, wherein a number of the first bad columns is less than or equal to a number of the first redundant columns, and wherein each of the first redundant columns stores replacement data for one of the first bad columns; and a second plane of flash memory cells comprising second non-redundant columns and second redundant columns, the second non-redundant columns having second bad columns, wherein a number of the second bad columns is greater than a number of the second redundant columns, and wherein at least a portion of the second redundant columns stores Error Correction Code (ECC) encoded data and a remaining portion of the second redundant columns stores replacement data for a portion of the second bad columns. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification