Methods, circuits, devices, and systems for sensing an NVM cell
Disclosed is a non-volatile memory (NVM) device including an array of NVM cells segmented into at least a first sector and a second sector and at least one sensing circuit to sense a state of a target NVM cell in the first sector using a reference current of the second sector received from at least a dynamic reference cell.
1. A method of operating a non-volatile memory (NVM) array, the method comprising:
receiving a target current on a first bitline from a target NVM cell in a first sector having a first group of wordlines, wherein the target NVM cell is in a data-cell sub-sector of the first sector;
generating a reference current, wherein generating the reference current comprises summing at least a first current and a second current on a second bitline, wherein the first current is from a first reference NVM cell in a second sector having a second group of wordlines, wherein the first reference NVM cell is in a reference sub-sector of the second sector, and wherein loads on the first bitline and the second bitline are matched; and
sensing a state of the target NVM cell, wherein sensing the state of the target NVM sell comprises comparing the target current to the reference current.
2. The method of claim 1 , wherein the second current is a digital current source current.
3. The method of claim 1 , wherein the second current is associated with a mini-array.
4. The method of claim 1 , wherein the second current is from a static reference cell of the second sector that is programmed to a predetermined level.
5. The method of claim 1 , wherein the first reference NVM cell is a dynamic reference cell that is intermittently erased and reprogrammed.
6. The method of claim 1 , wherein the first reference NVM cell is a dynamic reference cell that is substantially reflective of activity history of a typical NVM cell of the first sector.
7. The method of claim 1 , wherein the second current is from a second reference NVM cell in the reference sub-sector of the second sector.
8. The method of claim 7 , wherein the second reference NVM cell is a dynamic reference cell that is intermittently erased and reprogrammed.
9. The method of claim 7 , wherein the second reference NVM cell is a dynamic reference cell that is substantially reflective of activity history of a typical NVM cell of the first sector.
10. The method of claim 7 , wherein the second reference NVM cell is a dynamic reference cell that is sustained in a non-programmed state.
11. The method of claim 7 , wherein generating the reference current comprises connecting the first reference NVM cell and the second reference NVM cell to the second bitline.
12. A method of operating a non-volatile memory (NVM) array, the method comprising:
receiving a target current on a first bitline from a target NVM cell in a first sector having a first group of wordlines, wherein the target NVM cell is in a data-cell sub-sector of the first sector;
generating a reference current, wherein generating the reference current comprises summing at least two currents on a second bitline from at least two reference NVM cells in a second sector having a second group of wordlines, wherein the at least two reference NVM cells are in a reference sub-sector of the second sector, and wherein loads on the first bitline and the second bitline are matched; and
sensing a state of the target NVM cell, wherein sensing the state of the target NVM sell comprises comparing the target current to the reference current.
13. The method of claim 12 , wherein the at least two reference NVM cells include a static reference cell.
14. The method of claim 13 , wherein the method further comprises:
prior to receiving the target current and generating the reference current, programming the static reference cell to a predetermined level.
15. The method of claim 12 , wherein the at least two reference NVM cells include a dynamic reference cell.
16. The method of claim 15 , wherein the method further comprises:
prior to receiving the target current and generating the reference current, programming the dynamic reference cell to a predetermined level.
17. The method of claim 15 , wherein the method further comprises intermittently erasing and reprogramming the dynamic reference cell.
18. The method of claim 15 , wherein the dynamic reference cell is substantially reflective of activity history of a typical NVM cell of the first sector.
19. The method of claim 15 , wherein the dynamic reference cell is sustained in a non-programmed state.
20. The method of claim 12 , wherein generating the reference current comprises connecting the at least two reference NVM cells to the second bitline.