Freescale Semiconductor,inc.

Jon W Weilemann, Ii

Richard Eguchi

Chen He

Katrina M Prosperi

Daniel Hadad

Methods and systems are disclosed for imminent read failure detection based upon changes in error voltage windows for non-volatile memory (NVM) cells. In certain embodiments, data stored within an array of NVM cells is checked at a first time using a diagnostic mode and high/low read voltage sweeps to determine a first error voltage window where high/low uncorrectable errors are detected. Stored data is then checked at a second time using the diagnostic mode and high/low read voltage sweeps to determine a second error voltage window where high/low uncorrectable errors are detected. The difference between the error voltage windows are then compared against a voltage difference threshold value to determine whether or not to indicate an imminent read failure condition. An address sequencer, error correction code (ECC) logic, and a bias generator can be used to implement the imminent failure detection.

Imminent read failure detection based upon changes in error voltage windows for NVM cells

Methods and systems are disclosed for imminent read failure detection based upon unacceptable wear for non-volatile memory (NVM) cells. In certain embodiments, a first failure time is recorded when a first diagnostic mode detects an uncorrectable error within the NVM cell array using a first set of read voltage levels below and above a normal read voltage level. A second failure time is recorded when a second diagnostic mode detects an uncorrectable error within the NVM cell array using a second set of read voltage levels below and above a normal read voltage level. The first and second failure times are then compared against a threshold wear time value to determine whether or not an imminent read failure is indicated. The diagnostic modes can be run separately for erased NVM cell distributions and programmed NVM cell distributions to provide separate wear rate determinations.

Imminent read failure detection based upon unacceptable wear for NVM cells

Methods and systems are disclosed for imminent read failure detection using high/low read voltage levels. In certain embodiments, data stored within an array of non-volatile memory (NVM) cells is checked using read voltage levels below and above a normal read voltage level. An imminent read failure is then indicated if errors are detected within the same address for both voltage checks. Further, data stored can be checked using read voltage levels that are incrementally decreased below and incrementally increased above a normal read voltage level. An imminent read failure is then indicated if read errors are detected within the same address for both voltage sweeps and if high/low read voltage levels triggering faults differ by less than a predetermined threshold value. An address sequencer, error correction code (ECC) logic, and a bias generator can be used to implement the imminent failure detection.

Imminent read failure detection using high/low read voltage levels

A method and system are provided for determining an imminent failure of a non-volatile memory array. The method includes: performing a first array integrity read of the memory array until an error is detected; determining that the error is not error correction code (ECC) correctable, wherein a first word line voltage associated with the error is characterized as being a first threshold voltage; performing a second array integrity read of the memory array until all bits of the memory array indicate a predetermined state, wherein a second word line voltage associated with all of the bits indicating the predetermined state is a second threshold voltage; and comparing a difference between the first and second threshold voltages to a predetermined value.

Non-volatile memory (NVM) with imminent error prediction

A defect resistant EEPROM emulator () uses one or more redundant and/or spare blocks () in addition to active and alternate blocks () and stores a duplicate copy of EEPROM data records either in the active and redundant blocks or in duplicate rows in the active block to ensure that EEPROM emulation can continue without data loss in the event a catastrophic failure occurs within a block.

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Austin, TX, United States of America

Jon W Weilemann, Ii