Memory device and operating method therefor
A memory device includes a plurality of memory cells, bit lines connected to the plurality of memory cells, and page buffers coupled to the plurality of memory cells through the bit lines, and performing a read operation on the plurality of memory cells, wherein each of the page buffers comprises: a first latch controlling a bit line precharge operation during the read operation; and a second latch storing a result of a first sensing operation and a result of a second sensing operation performed after the first sensing operation, wherein a value stored in the second latch is inverted when the result of the first sensing operation and the result of second sensing operation are different from each other during the second sensing operation.
1. A memory device, comprising:
a plurality of memory cells;
bit lines connected to the plurality of memory cells; and
page buffers coupled to the plurality of memory cells through the bit lines, and performing a read operation on the plurality of memory cells,
wherein each of the page buffers comprises:
a first latch controlling a bit line precharge operation during the read operation; and
a second latch storing a result of a first sensing operation and a result of a second sensing operation performed after the first sensing operation,
wherein a value stored in the second latch is inverted when the result of the first sensing operation and the result of second sensing operation are different from each other during the second sensing operation,
wherein the first latch maintains a voltage level of the bit line at a precharged voltage level during the first sensing operation and the second sensing operation.
2. The memory device of claim 1 , wherein the value stored in the second latch is inverted when a memory cell is determined as an off-cell by the first sensing operation.
3. The memory device of claim 2 , wherein a target threshold voltage of the first sensing operation is greater than a target threshold voltage of the second sensing operation.
4. The memory device of claim 3 ,
wherein each of the first sensing operation and the second sensing operation includes a sense evaluation period, and
wherein the sense evaluation period of the first sensing operation is longer than the sense evaluation period of the second sensing operation.
5. The memory device of claim 1 , wherein the value stored in the second latch is inverted when a memory cell is determined as an on-cell by the first sensing operation.
6. The memory device of claim 5 , wherein a target threshold voltage of the first sensing operation is lower than a target threshold voltage of the second sensing operation.
7. The memory device of claim 1 , wherein a voltage of each of the bit lines during the read operation is maintained at a voltage set by the bit line precharge operation until the first sensing operation and the second sensing operation are terminated.
8. The memory device of claim 7 ,
wherein the plurality of memory cells are commonly coupled to a word line, and
wherein a voltage of the word line during the read operation is maintained at a voltage set during the bit line precharge operation until the first sensing operation and the second sensing operation are terminated.
9. The memory device of claim 8 ,
wherein each of the first sensing operation and the second sensing operation includes a sense evaluation period, and
wherein the sense evaluation period of the first sensing operation is different from the sense evaluation period of the second sensing operation.
10. A memory device, comprising:
a plurality of memory cells; and
page buffers performing a read operation on the plurality of memory cells,
wherein each of the page buffers includes:
a first latch controlling a bit line precharge operation during the read operation;
a second latch storing a result of a first sensing operation and a result of a second sensing operation subsequent to the first sensing operation during the read operation,
wherein a target threshold voltage of the first sensing operation is greater than a target threshold voltage of the second sensing operation, and
wherein the first latch maintains a voltage level of the bit line at a precharged voltage level during the first sensing operation and the second sensing operation.
11. The memory device of claim 10 , wherein a value stored in the latch is inverted when the result of the first sensing operation and the result of the second sensing operation are different from each other during the second sensing operation.
12. The memory device of claim 11 , wherein the value stored in the latch is inverted when a memory cell is determined as an off-cell during the first sensing operation.
13. The memory device of claim 11 , wherein the value stored in the latch is maintained when the result of the first sensing operation and the result of the second sensing operation are the same as each other during the second sensing operation.
14. The memory device of claim 11 ,
wherein each of the page buffers includes a sense out node of which a voltage is varied according to a threshold voltage of a memory cell, and
wherein the sense out node is coupled to a gate node of an n-type MOS transistor of the latch.
15. A method for operating a memory device, the method comprising:
precharging a bit line coupled to a memory cell;
performing a first sensing operation on the memory cell and storing in a latch as a first value, a sensed value by the first sensing operation; and
performing a second sensing operation on the memory cell and storing in the latch as a second value, a sensed value by the second sensing operation,
wherein a value stored in the latch is inverted when the first value and the second value are different from each other during the second sensing operation, and
wherein a voltage level of the bit line is maintained at a precharged voltage level during the first sensing operation and the second sensing operation.
16. The method of claim 15 , wherein a target threshold voltage of the first sensing operation is greater than a target threshold voltage of the second sensing operation.
17. The method of claim 16 , wherein the value stored in the latch is inverted when the memory cell is determined as an off-cell during the first sensing operation.
18. The method of claim 17 , wherein the value stored in the latch is maintained when the first value and the second value are the same as each other during the second sensing operation.
19. The method of claim 16 , wherein a bit line voltage set during the precharging of the bit line is maintained at a constant level during the first sensing operation and the second sensing operation.
20. The method of claim 19 , wherein a voltage of a word line coupled to the memory cell and set during the precharging of the bit line is maintained at a constant level during the first sensing operation and the second sensing operation.