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;
one or more managing circuits in communication with said plurality of non-volatile storage elements; and
a set of sensing circuits in communication with said one or more managing circuits and said plurality of non-volatile storage elements, said sensing circuits sense data stored in said non-volatile storage elements, each of said sensing circuits comprise:
a sense node in communication with a non-volatile storage element being read, said sensing circuit measures current conduction at said sense node to sense data stored in said non-volatile storage element being read,
a first capacitive device selectively connected to said sense node, and
a selection circuit connected to said first capacitive device, said selection circuit receives an indication from an adjacent non-volatile storage element and selectively connects said first capacitive device to said sense node based on said indication from said adjacent non-volatile storage element.
2. A non-volatile storage system according to claim 1 , wherein said sensing circuits further comprise a second capacitive device connected to said sense node.
3. A non-volatile storage system according to claim 1 , wherein:
said adjacent non-volatile storage element stores data for a first grouping and a second grouping;
said one or more managing circuits cause a reading of said second grouping for said adjacent non-volatile storage element;
if said second grouping for said adjacent non-volatile storage element stores a first value then said first capacitive device is connected to said sense node; and
if said second grouping for said adjacent non-volatile storage element stores a second value then said first capacitive device is not connected to said sense node.
4. A non-volatile storage system according to claim 1 , wherein:
said one or more managing circuits include a state machine.
5. A non-volatile storage system according to claim 1 , wherein:
said plurality of non-volatile storage elements are multi-state NAND flash memory devices.