Sensing in non-volatile storage using pulldown to regulated source voltage to remove system noise
View Patent ↗A pull down circuit pulls a bit line voltage to a regulated source voltage in a non-volatile storage device during a sense operation such as a verify operation which occurs during programming. The storage device may include NAND strings which have associated bit lines and sense components, and a common source line. When a selected storage element of a NAND string has been programmed to its intended state, the bit line is locked out during subsequent verify operations which occur for other NAND strings which are not yet locked out. The pull down device is coupled to each bit line and to the common source line, whose voltage is regulated at a positive DC level, to prevent coupling of system power bus (V SS ) noise from the locked out bit lines to the not yet locked out bit lines.
1. A non-volatile storage system, comprising:
a set of non-volatile storage elements;
a sense component associated with a sense node for the set of non-volatile storage elements;
a source associated with the set of non-volatile storage elements;
a voltage regulator for regulating a voltage level of the source; and
a pull down circuit for pulling the sense node to the source.
2. The non-volatile storage system of claim 1 , wherein:
the set of non-volatile storage elements is provided in a NAND string, and the sense component is selectively coupled to the NAND string during a sense operation.
3. The non-volatile storage system of claim 1 , further comprising:
a transistor which is set in a conductive state responsive to the sense component determining that at least one of the non-volatile storage elements has been programmed to an intended state, the sense node is pulled to the source via the transistor.
4. The non-volatile storage system of claim 1 , wherein:
the sense component is locked out from sensing after determining that at least one of the non-volatile storage elements has been programmed to an intended state.
5. The non-volatile storage system of claim 1 , wherein:
the voltage level of the source is regulated to a positive DC level.
6. The non-volatile storage system of claim 1 , wherein:
the voltage regulator comprises a feedback path coupled to the source.
7. The non-volatile storage system of claim 1 , wherein:
the voltage regulator is separate from a power supply of the non-volatile storage system.
8. The non-volatile storage system of claim 1 , further comprising:
at least one control circuit for controlling the pull down circuit to pull the sense node to the source during a sense operation.
9. The non-volatile storage system of claim 8 , wherein:
the sense operation comprises a verify operation which is part of a programming operation.
10. A non-volatile storage system, comprising:
a plurality of NAND strings, the NAND strings comprise non-volatile storage elements;
sense components associated with sense nodes of the NAND strings;
a common source associated with the NAND strings;
a voltage regulator for regulating a voltage level of the common source; and
pull down circuits for selectively pulling the sense nodes to the common source.
11. The non-volatile storage system of claim 10 , wherein the sense components include at least first and second sense components which are associated with first and second sense nodes, respectively, further comprising:
at least one control which, during a sense operation: (a) controls the first sense component to be active, (b) controls the second sense component to be inactive, and (c) controls one of the pull down circuits which is associated with the second sense node to pull the second sense node to the common source.
12. The non-volatile storage system of claim 11 , wherein:
the at least one control, during the sense operation, controls one of the pull down circuits which is associated with the first sense node to not pull the first sense node to the common source.
13. The non-volatile storage system of claim 12 , wherein:
during the sense operation, the first sense component senses that an associated non-volatile storage element has reached an intended programming state; and
during a subsequent sense operation, the at least one control circuit controls the one of the pull down circuits which is associated with first sense node to pull the first sense node to the common source.
14. The non-volatile storage system of claim 11 , wherein:
the sense operation comprises a verify operation which is part of a programming operation.
15. The non-volatile storage system of claim 10 , wherein:
the voltage regulator is separate from a power supply of the non-volatile storage system and comprises a feedback path coupled to the common source.
16. A method for operating a non-volatile storage system, comprising:
applying a programming voltage to a selected word line in the non-volatile storage system, the non-volatile storage system including a set of NAND strings, the NAND strings having associated sense nodes, the set of NAND strings being associated with a source; and
subsequent to applying the programming voltage, applying a verify voltage to the selected word line while regulating a voltage level of the source, and pulling a voltage of at least one of the sense nodes to the source.
17. The method of claim 16 , wherein:
the voltage level of the source is regulated to a positive DC level.
18. The method of claim 16 , wherein:
the regulating comprises controlling the voltage level using a feedback path coupled to the source.
19. The method of claim 16 , wherein:
the voltage level of the source is based on, but regulated separately from, a power supply voltage of the non-volatile storage system.
20. The method of claim 16 , wherein:
while applying the verify voltage, at least another one of the sense nodes is not pulled to the source.