Non-volatile memory and method with power-saving read and program-verify operations
A non-volatile memory device capable of reading and writing a large number of memory cells with multiple read/write circuits in parallel has features to reduce power consumption during read, and program/verify operations. A read or program verify operation includes one or more sensing cycles relative to one or more demarcation threshold voltages to determine a memory state. In one aspect, selective memory cells among the group being sensed in parallel have their conduction currents turned off when they are determined to be in a state not relevant to the current sensing cycle. In another aspect, a power-consuming period is minimized by preemptively starting any operations that would prolong the period. In a program/verify operation cells not to be programmed have their bit lines charged up in the program phase. Power is saved when a set of these bit lines avoids re-charging at every passing of a program phase.
1. In a nonvolatile memory having an array of nonvolatile memory cells, wherein each memory cell is accessible by a bit line and is programmable to a current conducting threshold voltage that corresponds to one of multiple memory states, a method of programming having cycles of alternate program phase and verify phase, comprising:
charging up bit lines of memory cells that are program inhibited to a predetermined voltage while not charging up bit lines of memory cells that are to be programmed at a beginning of the program phase; and
discharging the bit lines of memory cells that are to be programmed while not discharging the bit lines of the memory cells that are program inhibited at an end of the program phase.
2. The method as in claim 1 , wherein the nonvolatile memory has memory cells that individually store data as an amount of charge programmed into a charge storing element.
3. The method as in claim 2 , wherein the charge storing, element is a floating gate of a field effect transistor.
4. The method as in claim 2 , wherein the charge storing element is a dielectric layer in a field effect transistor.
5. The method as in claim 1 , wherein the non-volatile memory is a flash EEPROM.
6. The method as in claim 1 , wherein the nonvolatile memory is embodied in a memory card.
7. The method as in claim 1 , wherein the nonvolatile em memory is embedded in a computing device.
8. The method as in claim 1 , wherein the nonvolatile memory has memory cells that individually shire one bit of data.
9. The method as in claim 2 , wherein the nonvolatile memory has memory cells that individually store one hit of data.
10. The method as in claim 3 , wherein the nonvolatile memory has memory cells that individually store one bit of data.
11. The method as in claim 4 , wherein the nonvolatile memory has memory cells that individually store more than one hit of data.
12. The method as in claim 5 , wherein the nonvolatile memory has memory cells that individually store one bit of data.
13. The method as in claim 6 , wherein the nonvolatile memory has memory cells that individually store one bit of data.
14. The method as in claim 1 , wherein the nonvolatile memory has memory cells that individually store more than one bit of data.
15. The method as in claim 2 , wherein the nonvolatile memory has memory cells that individually store more than one bit of data.
16. The method as in claim 3 , wherein the nonvolatile memory has memory cells that individually store more than one bit of data.
17. The method as in claim 4 , wherein the nonvolatile memory has memory cells that individually store more than one bit of data.
18. The method as in claim 5 , wherein the nonvolatile memory has memory cells that individually store more than one bit of data.
19. The method as in claim 6 , wherein the nonvolatile memory has memory cells that individually store more than one bit of data.