Read operation for non-volatile storage that includes compensation for coupling
View Patent ↗Shifts in the apparent charge stored on a floating gate (or other charge storing element) of a non-volatile memory cell can occur because of the coupling of an electric field based on the charge stored in adjacent floating gates (or other adjacent charge storing elements). The problem occurs most pronouncedly between sets of adjacent memory cells that have been programmed at different times. To compensate for this coupling, the read process for a given memory cell will take into account the programmed state of an adjacent memory cell.
1. A non-volatile storage system, comprising:
a plurality of non-volatile storage elements including a first set of non-volatile storage elements and a second set of non-volatile storage elements adjacent to said first set of set of non-volatile storage elements, said first set of non-volatile storage elements and said second set of non-volatile storage elements store multiple groupings of data; and
one or more managing circuits in communication with said plurality of non-volatile storage elements, said one or more managing circuits read from said first set of non-volatile storage elements after first reading from said second set of non-volatile storage elements, said one or more managing circuits determine a reference value for reading said first non-volatile storage element based on a subset of said groupings of data capable of being stored in said second non-volatile storage element and subsequently read data stored in said first non-volatile storage element using said reference value.
2. A non-volatile storage system according to claim 1 , wherein:
said one or more managing circuits include a state machine, decoders and sense amplifiers.
3. A non-volatile storage system according to claim 2 , wherein each of said sense amplifiers comprise:
a sense node in communication with a non-volatile storage element being read, said sensing amplifier measures current conduction at said sense node to sense data stored in said non-volatile storage element being read,
a first capacitive device connected to said sense node,
a second capacitive device selectively connected to said sense node, and
a selection circuit connected to said second capacitive device, said selection circuit receives an indication from an adjacent non-volatile storage element and selectively connects said second capacitive device to said sense node based on said indication from said adjacent non-volatile storage element.
4. A non-volatile storage system according to claim 1 , wherein:
said non-volatile storage elements are multi-state NAND flash memory devices.
5. A non-volatile storage system according to claim 1 , wherein:
said multiple groupings of data include lower pages and upper pages; and
said one or more managing circuits determine a reference value by reading upper page data of said second non-volatile storage element, said reference value is based on said upper page data and not on lower page data for said second non-volatile storage element.
6. A non-volatile storage system according to claim 1 , wherein:
said first set of non-volatile storage elements include a second grouping of data programmed subsequent to writing to adjacent non-volatile storage elements for a first grouping of data.
7. A non-volatile storage system according to claim 1 , wherein:
said plurality of non-volatile storage elements include floating gates.
8. A non-volatile storage system according to claim 1 , wherein:
said plurality of non-volatile storage elements include dielectric regions for storing charge.
9. A non-volatile storage system, comprising:
a plurality of non-volatile storage elements including a first set of non-volatile storage elements and a second set of non-volatile storage elements adjacent to said first set of set of non-volatile storage elements; and
one or more managing circuits in communication with said plurality of non-volatile storage elements, said one or more managing circuits read a flag associated with said second set of non-volatile storage elements, said second set of non-volatile storage elements store multiple groupings of data, said flag indicates whether one of said groupings have been programmed for said second set of non-volatile storage elements, said one or more managing circuits read data from said first set of non-volatile storage elements using a first reference compare value if said flag indicates that said one of said groupings has not been programmed and reads said data from said first set of non-volatile storage elements using an offset to said first reference compare value if said flag indicates that said one of said groupings has been programmed.
10. A non-volatile storage system according to claim 9 , wherein:
said one or more managing circuits include a state machine, decoders and sense amplifiers.
11. A non-volatile storage system according to claim 9 , wherein said one or more managing circuits includes sense amplifiers, each of said sense amplifiers comprise:
a sense node in communication with a non-volatile storage element being read, said sensing amplifier measures current conduction at said sense node to sense data stored in said non-volatile storage element being read,
a first capacitive device connected to said sense node,
a second capacitive device selectively connected to said sense node, and
a selection circuit connected to said second capacitive device, said selection circuit receives an indication from an adjacent non-volatile storage element and selectively connects said second capacitive device to said sense node based on said indication from said adjacent non-volatile storage element.
12. A non-volatile storage system according to claim 9 , wherein:
said plurality of non-volatile storage elements are multi-state NAND flash memory devices.
13. A non-volatile storage system according to claim 9 , wherein:
said multiple groupings of data includes a lower page and an upper page; and
said flag indicates whether said upper page for said second set of non-volatile storage elements has been programmed.
14. A non-volatile storage system according to claim 9 , wherein:
said plurality of non-volatile storage elements store data programmed with respect to a second grouping of data subsequent to writing to adjacent non-volatile storage elements for a first grouping of data.