COMPENSATION OF BACK PATTERN EFFECT IN A MEMORY DEVICE
First Claim
1. A method for generating back pattern effect compensation in a memory device, the method comprising:
- measuring a back pattern effect level in a series string of memory cells;
generating an indication of the back pattern effect level; and
compensating a read operation of the series string of memory cells in response to the indication.
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Accused Products
Abstract
In one or more of the disclosed embodiments, a read operation is compensated for back pattern effect. A bit line current is generated by a read operation that biases the word lines. As part of a back pattern effect measurement phase, at predetermined time intervals an indication of the discharge status of the bit line is stored in a latch of a set of N latches coupled to each bit line. At the end of the measurement phase, the set of latches contains a multiple bit word that is an indication of the back pattern effect experienced by that particular series string of memory cells. This back pattern effect indication is used in subsequent read operations to adjust the timing of the operation.
8 Citations
20 Claims
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1. A method for generating back pattern effect compensation in a memory device, the method comprising:
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measuring a back pattern effect level in a series string of memory cells; generating an indication of the back pattern effect level; and compensating a read operation of the series string of memory cells in response to the indication. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for generating back pattern effect compensation in a non-volatile memory device, the method comprising:
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performing a sense operation on a series string of memory cells that is coupled to a bit line such that a bit line current is generated; generating a multiple bit word wherein each bit indicates a discharge status of the bit line during a different time period such that each bit is generated independently after each time period; reading a selected memory cell of the series string of memory cells; and compensating the reading in response to the multiple bit word wherein an increasing amount of back pattern effect results in a reduction of reading sense time. - View Dependent Claims (8, 9, 10, 11)
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12. A method for compensating a read operation for back pattern effects in a NAND flash memory device having a plurality of series strings of memory cells each coupled to a bit line, each series string coupled to N latches, the method comprising:
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performing a read operation on a first series string of memory cells to generate a bit line current, the read operation comprising; biasing each word line from a selected word line to a word line closest to a select gate drain line with a first voltage; and biasing each word line below the selected word line to the word line closest to a select gate source line with a second voltage that is greater than the first voltage; generating N strobe signals to enable a control transistor between the N latches and the series string of memory cells such that N bit line discharge status output signals are produced; generating N enable signals to latch each of the N bit line discharge status output signals into the N latches to produce a back pattern effect level indication; and adjusting a read time during a subsequent read operation in response to the back pattern effect level indication. - View Dependent Claims (13, 14)
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15. A solid state memory device comprising:
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an array of memory cells organized in rows of memory cells coupled to word lines and series strings of memory cells coupled to bit lines; and a set of N latches coupled to each series string of memory cells, wherein each set of latches is adapted to store an indication of a back pattern effect experienced by its respective series string of memory cells. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification