Nonvolatile memory apparatus and write control method thereof
View Patent ↗A nonvolatile memory apparatus includes a memory cell array, and a write operation controller configured to verify a write operation by comparing input data of the write operation controller to cell data written into the memory cell array, measure a resistance value after a first time is elapsed, and determine whether or not to re-perform the write operation according to the measured resistance value.
1. A nonvolatile memory apparatus comprising:
a memory cell array; and
a write operation controller configured to verify a write operation by comparing input data to the write operation controller to cell data written into the memory cell array, measure a resistance value after a preset time is elapsed, and determine whether or not to re-perform the write operation based on a comparison of the measured resistance value to a calculated reference resistance value.
2. The nonvolatile memory apparatus according to claim 1 , wherein the calculated reference resistance value is calculated by using an initial resistance value, an initial time when the initial resistance value is measured, a preset measurement time, and a constant of a phase change material.
3. The nonvolatile memory apparatus according to claim 2 , wherein the initial resistance value comprises a resistance value measured after the write operation verification.
4. The nonvolatile memory apparatus according to claim 2 , wherein, when the calculated reference resistance value is larger than the measured resistance value, the write operation controller is configured to terminate the write operation.
5. The nonvolatile memory apparatus according to claim 2 , wherein, when the calculated reference resistance value is smaller than the measured resistance value, the write operation controller is configured to re-perform the write operation.
6. The nonvolatile memory apparatus according to claim 1 , wherein the write operation controller measures the resistance value of a phase-change random access memory cell.
7. A nonvolatile memory apparatus comprising:
a memory cell array;
a write operation verification reader configured to verify whether or not input data provided to the write operation controller is identical to cell data written into the memory cell array; and
a write operation controller configured to verify a write operation by comparing the data read by the write operation verification reader to the input data, calculate a first reference resistance value corresponding to a first time, compare the first reference resistance value to a first measured resistance value, and determine whether or not to re-perform the write operation according to the first measured resistance value.
8. The nonvolatile memory apparatus according to claim 7 , wherein the first reference resistance value is calculated by using an initial resistance value, an initial time when the initial resistance value is measured, a first measurement time, and a constant of a phase change material.
9. The nonvolatile memory apparatus according to claim 8 , wherein the initial resistance value comprises a resistance value measured after a write operation verification performed by the write operation verification reader.
10. The nonvolatile memory apparatus according to claim 8 , wherein, when the first reference resistance value is larger than the first measured resistance value, the write operation controller is configured to terminate the write operation.
11. The nonvolatile memory apparatus according to claim 8 , wherein, when the first reference resistance value is smaller than the first measured resistance value, the write operation controller is configured to perform a second comparison based on a second reference resistance value.
12. The nonvolatile memory apparatus according to claim 8 , wherein the write operation controller measures the resistance value of a phase-change random access memory cell.
13. The nonvolatile memory apparatus according to claim 11 , wherein, when the second comparison is performed, the write operation controller is configured to calculate the second reference resistance value corresponding to a second time, compare the second reference resistance value to a second measured resistance value, and determine whether or not to re-perform the write operation according to the second measured resistance value.
14. A write control method of a nonvolatile memory apparatus, comprising:
writing data into a memory cell array when the data is inputted to the nonvolatile memory apparatus;
determining whether the write operation was normally performed or not;
when the write operation was normally performed, counting a first time and calculating a first reference resistance value corresponding to the first time; and
when the counting reaches the first time, comparing the first reference resistance value to a first measured resistance value measured at the first time, and determining whether or not to re-perform the write operation.
15. The write control method according to claim 14 , wherein, in the step of determining whether the write operation was normally performed or not,
when the data inputted to the nonvolatile memory apparatus is identical to data obtained by reading the data written into the memory cell array, the nonvolatile memory apparatus determines that the write operation was normally performed.
16. The write control method according to claim 15 , wherein, in the step of calculating the first reference resistance value corresponding to the first time,
the resistance value is calculated by using an initial resistance value, an initial time when the initial resistance value is measured, a first measurement time, and a constant of a phase change material.
17. The write control method according to claim 16 , wherein, in the step of determining whether or not to re-perform the write operation,
when the first reference resistance value is larger than the first measured resistance value, the nonvolatile memory apparatus terminates the write operation,
when the first reference resistance value is smaller than the first measured resistance value, the nonvolatile memory apparatus calculates a second reference resistance value at a second time, and subsequently compares the second reference resistance value to a second measured resistance value measured at the second time, and
when the second reference resistance value is smaller than the second measured resistance value, the nonvolatile memory apparatus re-performs the write operation.
18. The write control method according to claim 17 , wherein the second time is a time subsequent to the first time.