Non-volatile memory device and a read method thereof
A non-volatile memory device including: a page buffer configured to latch a plurality of page data constituting one bit page of a plurality of bit pages, and a control logic configured to compare results of a plurality of read operations performed in response to a high-priority read signal set to select one of a plurality of read signals included in the high-priority read signal set as a high-priority read signal, and determine a low-priority read signal corresponding to the high-priority read signal, wherein the high-priority read signal set is for reading high-priority page data, and the low-priority read signal is for reading low-priority page data.
1. A non-volatile memory device, comprising:
a page buffer configured to latch a plurality of page data constituting one bit page of a plurality of bit pages, and
a control logic configured to compare results of a plurality of read operations performed in response to a high-priority read signal set to select one of a plurality of read signals included in the high-priority read signal set as a high-priority read signal, and determine a low-priority read signal corresponding to the high-priority read signal, wherein the high-priority read signal set is for reading high-priority page data, and the low-priority read signal is for reading low-priority page data.
2. The non-volatile memory device according to claim 1 , wherein a level of the low-priority read signal corresponds to a level of the high-priority read signal.
3. The non-volatile memory device according to claim 1 , wherein a level of the low-priority read signal is different from a level of the high-priority read signal.
4. The non-volatile memory device according to claim 1 , wherein the control logic is configured to determine a level of the low-priority read signal, depending on a program state of the high-priority page data and a program state of the low-priority page data.
5. The non-volatile memory device according to claim 1 , wherein the control logic is configured to determine a level of the low-priority read signal by comparing a spread direction of distribution of the high-priority page data and a spread direction of distribution of the low-priority page data.
6. The non-volatile memory device according to claim 5 , wherein, when the spread direction of distribution of the high-priority page data is opposite to the spread direction of distribution of the low-priority page data, the control logic is configured to shift a level of the high-priority read signal in a direction opposite to the spread direction of distribution of the high-priority page data to determine the level of the low-priority read signal.
7. The non-volatile memory device according to claim 6 , wherein, when a program state of the low-priority page data is higher than a program state of the high-priority page data, the control logic is configured to shift the level of the high-priority read signal in a lower program direction to determine the level of the low-priority read signal.
8. The non-volatile memory device according to claim 6 , wherein, when the program state of the low-priority page data is lower than the program state of the high-priority page data, the control logic is configured to shift the level of the high-priority read signal to a higher program direction to determine the level of the low-priority read signal.
9. The non-volatile memory device according to claim 5 , wherein, when the spread direction of distribution of the high-priority page data is identical to the spread direction of distribution of the low-priority page data, the control logic is configured to compare a spread degree of distribution of the high-priority page data to a spread degree of distribution of the low-priority page data.
10. The non-volatile memory device according to claim 9 , wherein, when the spread degree of distribution of the high-priority page data is higher than the spread degree of distribution of the low-priority page data, the control logic is configured to shift a level of the high-priority read signal in a direction opposite to the spread direction of distribution of the high-priority page data to determine the level of the low-priority read signal.
11. The non-volatile memory device according to claim 9 , wherein, when the spread degree of distribution of the high-priority page data is lower than the spread degree of distribution of the low-priority page data, the control logic is configured to shift a level of the high-priority read signal in the spread direction of distribution of the high-priority page data to determine the level of the low-priority read signal.
12. The non-volatile memory device according to claim 1 , wherein the control logic is configured to change a latching time of the page buffer to vary a level of the low-priority read signal, during a read operation of the low-priority page data following a read operation of the high-priority page data.
13. The non-volatile memory device according to claim 12 , wherein the control logic is configured to change the latching time of the page buffer to vary the level of the low-priority read signal, during a read operation of a first low-priority page data among the low-priority page data.
14. The non-volatile memory device according to claim 13 , wherein the control logic is configured to change a level of a read voltage provided to memory cells connected to the page buffer to vary the level of the low-priority read signal, during a read operation of page data following the read operation of the first low-priority page data.
15. A non-volatile memory device, comprising:
a page buffer including a latch set for latching a plurality of page data constituting one bit page of a plurality of bit pages; and
a control logic for comparing results of a plurality of read operations performed in response to a plurality of high-priority read signal sets to select a high-priority read signal in each of the high-priority read signal sets, and for determining a level of a low-priority read signal, depending on a level of the high-priority read signal selected in each of the high-priority read signal sets, during a read operation of low-priority page data following a read operation of high-priority page data, wherein the plurality of high-priority read signal sets are for reading the high-priority page data.
16. The non-volatile memory device according to claim 15 , wherein the high-priority page data comprise a first high-priority page data, obtained by reading with a first high-priority read signal set among the high-priority read signal sets, and a second high-priority page data, obtained by reading with a second high-priority read signal set among the high-priority read signal sets, after the first high-priority page data is obtained.
17. The non-volatile memory device according to claim 16 , wherein the first high-priority page data and the second high-priority page data correspond to page data for identifying each of a highest program state and a lowest program state among the plurality of page data constituting the one bit page.
18. The non-volatile memory device according to claim 16 , wherein, when a level of a first high-priority read signal selected from the first high-priority read signal set is identical to a level of a second high-priority read signal selected from the second high-priority read signal set, the low-priority read signal has the same level as the first high-priority read signal and the second high-priority read signal.
19. The non-volatile memory device according to claim 16 , wherein, when a level of a first high-priority read signal selected from the first high-priority read signal set is different from a level of a second high-priority read signal selected from the second high-priority read signal set, and the level of the first high-priority read signal is adjacent to the level of the second high-priority read signal, the low-priority read signal has the same level as the first high-priority read signal or the second high-priority read signal.
20. The non-volatile memory device according to claim 19 , wherein the level of the low-priority read signal is determined, depending on a number of memory cells counted by the first high-priority read signal and the second high-priority read signal.
21. The non-volatile memory device according to claim 19 , wherein the level of the low-priority read signal is determined, depending on a position of the first high-priority page data, the second high-priority page data, and the low-priority page data.
22. The non-volatile memory device according to claim 16 , wherein, when a level of a first high-priority read signal selected from the first high-priority read signal set is different from a level of a second high-priority read signal selected from the second high-priority read signal set, and an odd number of levels are between the level of the first high-priority read signal and the level of the second high-priority read signal, the low-priority read signal has a level at an intermediate level of the odd number of levels.
23. The non-volatile memory device according to claim 16 , wherein, when a level of a first high-priority read signal selected from the first high-priority read signal set is different from a level of a second high-priority read signal selected from the second high-priority read signal set, and an even number of levels are between the level of the first high-priority read signal and the level of the second high-priority read signal, the low-priority read signal has the same level as one of the even number of levels, depending on a position of the first high-priority page data, the second high-priority page data, and the low-priority page data.
24. A read method of a non-volatile memory device, comprising:
comparing results of a plurality of read operations performed according to a high-priority read signal set,
selecting a high-priority read signal corresponding to high-priority page data from the high-priority read signal set; and
determining low-priority read signals for reading low-priority page data, depending on the level of the high-priority read signal,
wherein levels of the low-priority read signals are determined by comparing a spread direction of distribution of the high-priority page data and a spread direction of distribution of the low-priority page data.
25. The read method of a non-volatile memory device according to claim 24 , further comprising shifting sequentially the level of the high-priority read signal in a direction opposite to the spread direction of distribution of the high-priority page data to determine the levels of the low-priority read signals, when the spread direction of distribution of the high-priority page data is opposite to the spread direction of distribution of the low-priority page data.
26. The read method of a non-volatile memory device according to claim 24 , further comprising comparing a spread degree of distribution of the high-priority page data to a spread degree of distribution of the low-priority page data to determine the levels of the low-priority read signals, when the spread direction of distribution of the high-priority page data is identical to the spread direction of distribution of the low-priority page data.
27. A non-volatile memory device, comprising:
a page buffer configured to latch a plurality of page data constituting one bit page of a plurality of bit pages, and
a control logic configured to perform an On-Chip Valley Search (OCVS) reading operation to identify high-priority page data, and a normal reading operation to identify low-priority page data, wherein a low-priority read signal is selected for the normal reading operation by using a high-priority read signal from the high-priority page data.
28. The non-volatile memory device of claim 27 , wherein, in the OCVS reading operation, the control logic is configured to compare results of a plurality of read operations to select the high-priority read signal.
29. The non-volatile memory device of claim 28 , wherein, in the normal reading operation, the low-priority page data is read according to the low-priority read signal.