US 7,352,635 B2Granted

Method for remote redundancy for non-volatile memory

AssigneeSanDisk Corporation

InventorRaul-Adrian Cernea

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Abstract

A memory has defective locations in its user portion replaceable by redundant locations in a redundant portion. Data latches in column circuits of user and redundant portions allow data sensed from or to be written to a memory to be exchanged with a data bus. A remote redundancy scheme has the redundant data available from a central buffer accessible by any number of column circuits. Redundant data buffer circuits enable bus exchange with data from the user data latches except for defective locations when data are taken from the central buffer. In this way only addressing for the user portion is used for bus exchange. Also, accessibility to the redundant data will not be restricted by the locations of the column circuits relative to the redundant data latches and the buffered redundant data can be accessed at a finer granularity than that imposed by the column circuits.

Claims12

Dependent claims

In a non-volatile memory array partitioned into an user array portion and a redundant array portion such that a defective location in the user array portion is replaceable by a corresponding redundant location in the redundant array portion, a method of reading data from a group of memory locations straddling both the user and redundant array portions of the memory, comprising:

providing a group of access circuits including a group of data latches for latching data associated with both the user array portion and the redundant array portion;
providing a data bus;
buffering addresses of defective locations of the user array portion in a defect map buffer;
buffering redundant data from the data latches of the redundant array portion in a redundant data buffer;
and
enabling exchange of data between the data bus and the user portion data latches in response to a current address of the user array portion that does not correspond to a defective location in the defect map buffer, and enabling exchange of data between the data bus and a corresponding redundant data in the redundant data buffer in response to a current address of the user array portion that corresponds to a defective location in the defect map buffer.

3 more elements

Dependencies are inferred from the claim text.