REFRESH METHOD, REFRESH ADDRESS GENERATOR, VOLATILE MEMORY DEVICE INCLUDING THE SAME
First Claim
1. A refresh method for a volatile memory device including a plurality of memory cells arranged in an array having a plurality of rows and a plurality of columns, each row corresponding to a respective address, the refresh method comprising:
- refreshing memory cells of a first set of rows of the array at a first refresh rate having a first refresh period, the first refresh rate being a lower rate having a longer refresh period than a second refresh rate having a second refresh period, wherein each memory cell in the first set of rows of the array has a retention time longer than the first refresh period; and
refreshing memory cells of a second set of rows of the array at a third refresh rate having a third refresh period, the third refresh rate being a higher rate having a shorter refresh period than the second refresh rate having the second refresh period, wherein at least one memory cell of each row of the second set of rows has a retention time longer than the third refresh period and shorter than the first refresh period,wherein the second refresh period corresponds to a refresh period defined in a standard for the volatile memory device.
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Abstract
A refresh method for a volatile memory device includes refreshing memory cells of a first set of rows of an array at a first refresh rate having a first refresh period, the first refresh rate being a lower rate having a longer refresh period than a second refresh rate having a second refresh period, wherein each memory cell in the first set of rows of the array has a retention time longer than the first refresh period; and refreshing memory cells of a second set of rows of the array at a third refresh rate having a third refresh period, the third refresh rate being a higher rate having a shorter refresh period than the second refresh rate having the second refresh period, wherein at least one memory cell of each row of the second set of rows has a retention time longer than the third refresh period and shorter than the first refresh period. The second refresh period corresponds to a refresh period defined in a standard for the volatile memory device.
14 Citations
20 Claims
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1. A refresh method for a volatile memory device including a plurality of memory cells arranged in an array having a plurality of rows and a plurality of columns, each row corresponding to a respective address, the refresh method comprising:
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refreshing memory cells of a first set of rows of the array at a first refresh rate having a first refresh period, the first refresh rate being a lower rate having a longer refresh period than a second refresh rate having a second refresh period, wherein each memory cell in the first set of rows of the array has a retention time longer than the first refresh period; and refreshing memory cells of a second set of rows of the array at a third refresh rate having a third refresh period, the third refresh rate being a higher rate having a shorter refresh period than the second refresh rate having the second refresh period, wherein at least one memory cell of each row of the second set of rows has a retention time longer than the third refresh period and shorter than the first refresh period, wherein the second refresh period corresponds to a refresh period defined in a standard for the volatile memory device. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10)
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5. The method of 4, wherein the counter-based refresh includes generating a refresh address at each increase of a counter value.
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11. A refresh method for a volatile memory device including a plurality of memory cells arranged in an array having a plurality of rows and a plurality of columns, each row corresponding to a respective address, the refresh method comprising:
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refreshing memory cells of a first set of rows of the array at a first refresh rate having a first refresh period, based on a counter-based refresh, wherein the memory cells of the first set of rows have a retention time longer than the first refresh period; and refreshing memory cells of a second set of rows of the array at a second refresh rate having a second refresh period, based on a table-based refresh, the second refresh rate being a higher rate having a shorter refresh period than the first refresh period, wherein at least one memory cell of each row of the second set of rows has a retention time longer than the second refresh period and shorter than the first refresh period. - View Dependent Claims (12, 13, 15, 16)
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14. The method of 11, wherein the counter-based refresh includes generating a first refresh address at each increase of a counter value.
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17. A method of performing a refresh operation in a memory device including a memory array having rows and columns, comprising:
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performing a first refresh sub-operation by cycling through all of the rows of the memory array consecutively at equally spaced first time intervals based on a counter, such that each row of the first refresh sub-operation is refreshed subsequent to an adjacent previously refreshed row of the first refresh sub-operation after an occurrence of the first time interval, wherein the time between two refreshes of the same row in the first refresh sub-operation is referred to as a refresh cycle; and performing a second refresh sub-operation within the refresh cycle on a plurality of first rows of the memory array based on information stored in a table, and not performing the second refresh sub-operation within the refresh cycle on a plurality of second rows of the memory array, wherein the plurality of first rows each include at least one cell that has a first retention time, and wherein the plurality of second rows include a plurality of cells that have retention times longer than the first retention time. - View Dependent Claims (18, 19, 20)
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Specification