Method for current sensing with biasing of source and P-well in non-volatile storage
View Patent ↗Current sensing is performed in a non-volatile storage device for a non-volatile storage element. A voltage is applied to a selected word line of the first non-volatile storage element, and source and p-well voltages are applied to a source and a p-well, respectively, associated with the non-volatile storage element. The source and p-well voltages are regulated at respective positive DC levels to avoid a ground bounce, or voltage fluctuation, which would occur if the source voltage at least was regulated at a ground voltage. A programming condition of the non-volatile storage element is determined by sensing a current in a NAND string of the non-volatile storage element. The sensing can occur quickly since there is no delay in waiting for the ground bounce to settle.
1. A method for operating a non-volatile storage system, comprising:
applying at least a first voltage to a selected word line which is associated with at least a first non-volatile storage element in a set of non-volatile storage elements;
regulating a source voltage at a positive DC level for a source which is associated with the at least a first non-volatile storage element during at least a portion of a time in which the at least a first voltage is applied; and
determining whether the at least a first non-volatile storage element is in a conductive or non-conductive state using current sensing while applying the at least a first voltage and during the regulating.
2. The method of claim 1 , further comprising:
regulating a p-well voltage at a positive DC level for a p-well which is associated with the at least a first non-volatile storage element during at least a portion of a time in which the at least a first voltage is applied.
3. The method of claim 2 , wherein:
the source and p-well voltages are regulated at different DC levels.
4. The method of claim 2 , wherein:
the source and p-well voltages are regulated at a common DC level.
5. The method of claim 1 , further comprising:
grounding a voltage of a p-well which is associated with the at least a first non-volatile storage element during at least a portion of a time in which the at least a first voltage is applied.
6. The method of claim 1 , wherein:
the at least a first non-volatile storage element has a negative threshold voltage.
7. The method of claim 1 , wherein:
the at least a first non-volatile storage element is in a NAND string and the source voltage is applied to a source side of the NAND string.
8. The method of claim 1 , wherein:
the using the current sensing comprises determining a voltage drop which is proportional to a fixed current which flows through the at least a first non-volatile storage element and sinks into the source when the at least a first non-volatile storage element is in the conductive state.
9. The method of claim 1 , wherein:
the selected word line is associated with non-volatile storage elements in a plurality of adjacent NAND strings;
the source is associated with each of the non-volatile storage elements; and
the method further comprises determining, in concurrent sensing operations, whether each of the non-volatile storage elements is in the conductive or non-conductive state using current sensing while applying the at least a first voltage and during the regulating.
10. The method of claim 1 , wherein:
during the current sensing, a fixed current flows through the at least a first non-volatile storage element and sinks into the source when the at least a first non-volatile storage element is in the conductive state.
11. A method for operating a non-volatile storage system, comprising:
applying at least a first voltage to a selected word line of at least a first non-volatile storage element in a set of non-volatile storage elements;
regulating source and p-well voltages at respective positive DC levels for a source and p-well, respectively, which are associated with the at least a first non-volatile storage element during at least a portion of a time in which the at least a first voltage is applied; and
sensing a programming condition of the at least a first non-volatile storage element relative to a compare point using current sensing, while applying the at least a first voltage and regulating the source and p-well voltages.
12. The method of claim 11 , wherein:
the source and p-well voltages are regulated at different positive DC levels.
13. The method of claim 11 , wherein:
the source and p-well voltages are regulated at a common positive DC level.
14. The method of claim 11 , wherein:
the programming condition is defined with respect to a negative threshold voltage, and the at least a first voltage is a positive voltage.
15. The method of claim 11 , wherein:
the programming condition is defined with respect to a positive threshold voltage.
16. A method for operating a non-volatile storage system, comprising:
providing a potential of a drain associated with at least a first non-volatile storage element above a potential of a source associated with the at least a first non-volatile storage element;
applying at least a first voltage to a selected word line of the at least a first non-volatile storage element;
regulating source and p-well voltages at respective positive DC levels for a source and p-well, respectively, which are associated with the at least a first non-volatile storage element during at least a portion of a time in which the at least a first voltage is applied;
while applying the at least a first voltage, and regulating the source and p-well voltages, performing current sensing with respect to a current which flows through the at least a first non-volatile storage element and sinks into the source; and
determining a programming condition of the at least a first non-volatile storage element according to the current sensing.
17. The method of claim 16 , wherein:
the source and p-well voltages are regulated at different positive DC levels.
18. The method of claim 16 , wherein:
the source and p-well voltages are regulated at a common positive DC level.
19. The method of claim 16 , wherein:
the programming condition is defined with respect to a negative threshold voltage, and the at least a first voltage is a positive voltage.
20. The method of claim 16 , wherein:
the programming condition is defined with respect to a positive threshold voltage.