US20100290282A1 - Method and system for adaptively finding reference voltages for reading data from a mlc flash memory - Google Patents
Method and system for adaptively finding reference voltages for reading data from a mlc flash memory Download PDFInfo
- Publication number
- US20100290282A1 US20100290282A1 US12/464,240 US46424009A US2010290282A1 US 20100290282 A1 US20100290282 A1 US 20100290282A1 US 46424009 A US46424009 A US 46424009A US 2010290282 A1 US2010290282 A1 US 2010290282A1
- Authority
- US
- United States
- Prior art keywords
- threshold voltage
- flash memory
- initial
- voltages
- data
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/56—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency
- G11C11/5621—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency using charge storage in a floating gate
- G11C11/5642—Sensing or reading circuits; Data output circuits
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2211/00—Indexing scheme relating to digital stores characterized by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C2211/56—Indexing scheme relating to G11C11/56 and sub-groups for features not covered by these groups
- G11C2211/562—Multilevel memory programming aspects
- G11C2211/5621—Multilevel programming verification
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C2211/00—Indexing scheme relating to digital stores characterized by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C2211/56—Indexing scheme relating to G11C11/56 and sub-groups for features not covered by these groups
- G11C2211/563—Multilevel memory reading aspects
- G11C2211/5634—Reference cells
Definitions
- the present invention generally relates to multi-level cell (MLC) flash memory, and more particularly to method and system for adaptively finding reference voltages for reading data from the MLC flash memory.
- MLC multi-level cell
- Flash memory is a non-volatile solid state memory device that can be electrically erased and reprogrammed, and is a specific type of electrically erasable programmable read-only memory (EEPROM) device.
- EEPROM electrically erasable programmable read-only memory
- Conventional flash memory stores a single bit of information in each memory cell such that each memory cell can be programmed to assume two possible states.
- the conventional flash memory is thus commonly referred to as single-level cell (SLC) flash memory or single-bit cell (SBC) flash memory.
- SLC single-level cell
- SBC single-bit cell
- Modern flash memory is capable of storing two or more bits of information in each memory cell such that each memory cell can be programmed to assume more than two possible states.
- the modern flash memory is thus commonly referred to as multi-level cell (MLC) flash memory or multi-bit cell (MBC) flash memory.
- MLC multi-level cell
- MLC multi-bit cell
- FIG. 1 shows a common distribution of the threshold voltage for a typical MLC flash memory (a three-bit cell flash memory is exemplified here).
- the entire voltage range (e.g., Vmin through Vmax) is divided into a number of regions (e.g., eight regions in the example), each region corresponding to one state.
- the number of cells of each threshold voltage is collected as illustrated.
- the threshold voltage of a cell is compared to reference voltages (e.g., V 1 , V 2 , etc. in the figure) to determine its state. For example, if the threshold voltage of a cell is within the reference voltages V 4 and V 5 , the “011” state is thus determined and read from the flash memory.
- the reference voltages for reading data from the traditional MLC flash memory are constant.
- the threshold voltage distribution (e.g., the distribution in FIG. 1 ) may probably change after the flash memory has been subject to a predetermined number of program/erase cycles or/and a predetermined data retention time has elapsed.
- the initial distribution represented by the (dotted) curve 20 with reference voltage V 4 may be suffered from retention issue after a long time not going through program/erase cycle, and therefore drifted downward to a shifted distribution represented by the (solid) curve 22 with a new reference voltage V 4 ′. Errors probably incur if the reference voltage V 4 of the initial distribution 20 is still used (while the new reference voltage V 4 ′ is unknown) to read data from the flash memory.
- an initial threshold voltage distribution includes data pairs ⁇ N,V>, each including normalized number N of cells of the flash memory and corresponding threshold voltage V in the initial threshold voltage distribution.
- the normalized number N 1 of the cells corresponding to a given threshold voltage V 1 in a shifted threshold voltage distribution to be determined is obtained.
- initial reference voltage or voltages of the initial threshold voltage distribution are shifted with an amount approximate to difference between the threshold voltage V 2 and the given threshold voltage V 1 , thereby resulting in new reference voltage or voltages for reading the data from the MLC flash memory.
- total number N of cells of the flash memory above a reference threshold voltage of a reference state in an initial threshold voltage distribution is provided. Subsequently, search to find a threshold voltage Va corresponding to a state above which totals number of the cells is approximate to the total number N. Finally, initial reference voltage or voltages of the initial threshold voltage distribution are shifted with an amount approximate to difference between the threshold voltage Va and the reference threshold voltage, thereby resulting in new reference voltage or voltages for reading the data from the MLC flash memory.
- FIG. 1 shows a common distribution of the threshold voltage for a typical MLC flash memory
- FIG. 2 shows that a portion of the threshold voltage distribution in FIG. 1 changes after the flash memory has been subject to program/erase cycles or/and data retention time has elapsed;
- FIG. 3A shows an exemplary threshold voltage distribution of a MLC flash memory, illustrating the aspect according to the first embodiment of the present invention
- FIG. 3B shows a flow diagram corresponding to the aspect of the first embodiment of FIG. 3A ;
- FIG. 4A shows an exemplary threshold voltage distribution of a MLC flash memory, illustrating the aspect according to the second embodiment of the present invention
- FIG. 4B shows a flow diagram corresponding to the aspect of the second embodiment of FIG. 4A ;
- FIG. 5 shows a block diagram illustrating a memory system for adaptively finding proper reference voltages for reading data from a MLC flash memory according to one embodiment of the present invention.
- FIG. 3A shows an exemplary threshold voltage distribution of a multi-level cell (MLC) flash memory, illustrating the aspect according to the first embodiment of the present invention.
- FIG. 3B shows a flow diagram corresponding to the aspect of the first embodiment.
- (solid) curve 300 represents the initial distribution of the threshold voltage of a state of the flash memory.
- Another (dotted) curve 302 in FIG. 3A represents a threshold voltage distribution after the flash memory has been subject to a predetermined number of program/erase cycles or/and a predetermined data retention time has elapsed.
- the curve 302 is supposed to shift or drift downward (e.g., leftward in the figure) as shown due to the cycle/retention issue after a long time not going through program/erase cycle. It is noted that only one state is shown while other states are omitted in the figure for brevity.
- the flash memory is requested by a read command (the step 31 )
- the number of cells for example, N 1
- a threshold voltage for example, V 1
- N 1 the number of cells of a state or states from a spare area of the flash memory which we store at program phase. If the number of cells at that state is N, the value N 1 is normalized (in the step 32 ) to be N 1 /N.
- normalized ⁇ N,V> data of the initial distribution represented by the curve 300 are retrieved.
- the known normalized ⁇ N,V> data is stored beforehand, for example, in a look up table (LUT), where N represents the normalized number of cells and V represents the corresponding threshold voltage.
- the step 34 compare the normalized ⁇ N 1 ,V 1 > of the shifted distribution 302 with the normalized ⁇ N,V> of the initial distribution 300 in order to find the threshold voltage V 2 in the initial threshold voltage distribution 300 which has a corresponding normalized number N 2 of cells approximate the value N 1 .
- the search for finding the threshold voltage V 2 may utilize a conventional search method.
- the term “approximate” may mean that the number to be searched is within a predetermined range of a target value N 1 , and may include the case in which the searched number is equal to the target value.
- a new reference voltage for reading data from the MLC flash memory due to the cycle/retention issue is obtained by shifting the original reference voltage downward with the amount of the difference of V 2 and V 1 (i.e., V 2 ⁇ V 1 ).
- all reference voltages are shifted with the same amount V 2 ⁇ V 1 .
- different reference voltage is shifted with different amount. For example, if the calculated shift amount for the reference voltage V 7 is 1 volts, then the shift amount for the reference voltage V 6 may be 0.9 volts, and the shift amount for the reference voltage V 5 may be 0.8 volts.
- FIG. 4A shows an exemplary threshold voltage distribution of a MLC flash memory, illustrating the aspect according to the second embodiment of the present invention.
- FIG. 4B shows a flow diagram corresponding to the aspect of the second embodiment.
- (solid) curves 400 represent the initial distribution of the threshold voltage of the states of the flash memory.
- Another (dotted) curves 402 in the FIG. 4A represent a threshold voltage distribution after the flash memory has been subject to a predetermined number of program/erase cycles or/and a predetermined data retention time has elapsed.
- the curves 402 are supposed to shift or drift downward (e.g., leftward in the figure) as shown due to the cycle/retention issue after a long time not going through program/erase cycle.
- the step 41 after the flash memory is requested by a read command (the step 41 ), the total number Na of the cells above a specific state (e.g., above the threshold voltage Va) of the shifted distribution 402 is obtained (the step 42 ). Subsequently, search to find a reference state (such as the program verify voltage Vpv in FIG. 4A ), above which the total number N of cells is equal or approximate to Na.
- the number N is compared with the number Na (the step 45 ). If the difference (N ⁇ Na) is not less than a predetermined value m (such as the acceptable error tolerance) and the maximum world line voltage has not been reached (the step 46 ), next word line voltage is then set (the step 47 ).
- the steps 44 - 45 iterate until the difference (N ⁇ Na) is less than the predetermined m (the step 45 ) or the maximum world line voltage has been reached (the step 46 ).
- a new reference voltage for reading data from the MLC flash memory due to the cycle/retention issue is obtained by shifting the original reference voltage downward with the amount of the difference of Vpv and Va (i.e., Vpv ⁇ Va). In one exemplary embodiment, all reference voltages are shifted with the same amount Vpv-Va. In another exemplary embodiment, different reference voltage is shifted with different amount.
- the embodiments of the present invention associate a first threshold voltage (e.g., V 2 in FIG. 3A or Vpv in FIG. 4A ) in the initial distribution with a second threshold voltage (e.g., V 1 in FIG. 3A or Va in FIG. 4A ) in a shifted distribution to be determined, such that the information (e.g., the normalized number N 1 of cells in FIG. 3A or the total number Na of cells above a state in FIG. 4A ) corresponding to the second threshold voltage is approximate to the information corresponding to the first threshold voltage.
- a first threshold voltage e.g., V 2 in FIG. 3A or Vpv in FIG. 4A
- a second threshold voltage e.g., V 1 in FIG. 3A or Va in FIG. 4A
- the difference between the first threshold voltage and the second threshold voltage is then determined and subsequently utilized to correct the reference voltage(s) of the initial threshold voltage distribution due to the cycle/retention issue. It is worthy of noting that, as the effort to obtain the information and determine the difference concerns only basic calculations, the embodiments of the present invention may not only effectively but also economically find proper reference voltages for reading data from a MLC flash memory without much latency.
- FIG. 5 shows a block diagram illustrating a memory system 5 for adaptively finding proper reference voltages for reading data from a MLC flash memory according to one embodiment of the present invention.
- the memory system 5 may be adapted to the first embodiment (Fir. 3 A/B) or the second embodiment (FIG. 4 A/B).
- the memory system 5 includes a flash memory 50 and a memory controller 52 .
- Data may be written (programmed) to or read from the flash memory 50 from/to a host (not shown) through the memory controller 52 .
- the flash memory 50 the data being written to or read from the memory cells (not shown) of the flash memory 50 may be temporarily stored in a page buffer 500 , and operation and timing of the flash memory 50 is managed by control logic 502 .
- a data buffer 520 is used for temporarily storing data and for interfacing with the flash memory 50
- control logic 522 is used for managing the operation and timing of the memory controller 52 .
- the memory controller 52 further includes a data pair ⁇ N,V> generator 524 that generates the normalized number N 1 of cells corresponding to respective threshold voltage V 1 (in the first embodiment) or generates the total number Na of cells above respective state (in the second embodiment).
- the memory controller 52 also includes a reference voltage decision device 528 that associates a first threshold voltage (e.g., V 2 in FIG. 3A or Vpv in FIG. 4A ) in the initial distribution with a second threshold voltage (e.g., V 1 in FIG. 3A or Va in FIG. 4A ) in a shifted distribution to be determined, such that the information (e.g., the normalized number N 1 of cells in FIG. 3A or the total number Na of cells above a state in FIG.
- the blocks ( 500 - 528 ) of the memory system 5 may be implemented using hardware technique (such as circuit) or software technique (such as program run on a microcontroller) or their combination.
Abstract
Description
- 1. Field of the Invention
- The present invention generally relates to multi-level cell (MLC) flash memory, and more particularly to method and system for adaptively finding reference voltages for reading data from the MLC flash memory.
- 2. Description of the Prior Art
- Flash memory is a non-volatile solid state memory device that can be electrically erased and reprogrammed, and is a specific type of electrically erasable programmable read-only memory (EEPROM) device. Conventional flash memory stores a single bit of information in each memory cell such that each memory cell can be programmed to assume two possible states. The conventional flash memory is thus commonly referred to as single-level cell (SLC) flash memory or single-bit cell (SBC) flash memory. Modern flash memory is capable of storing two or more bits of information in each memory cell such that each memory cell can be programmed to assume more than two possible states. The modern flash memory is thus commonly referred to as multi-level cell (MLC) flash memory or multi-bit cell (MBC) flash memory.
- In the MLC flash memory, data of different state are written to the flash memory (which is commonly referred as programming the flash memory) by storing different amount of charge in the floating gate of the flash memory. As the charge in the floating gate specifically determines the corresponding threshold voltage, the data can then be read from the MLC flash memory according to their different threshold voltage. Due to variations among the memory cells during the manufacture, operation or according to other factors, the threshold voltage of each state is not a constant value but a range.
FIG. 1 shows a common distribution of the threshold voltage for a typical MLC flash memory (a three-bit cell flash memory is exemplified here). The entire voltage range (e.g., Vmin through Vmax) is divided into a number of regions (e.g., eight regions in the example), each region corresponding to one state. The number of cells of each threshold voltage is collected as illustrated. When the flash memory is being read, the threshold voltage of a cell is compared to reference voltages (e.g., V1, V2, etc. in the figure) to determine its state. For example, if the threshold voltage of a cell is within the reference voltages V4 and V5, the “011” state is thus determined and read from the flash memory. - The reference voltages for reading data from the traditional MLC flash memory are constant. In practice, however, the threshold voltage distribution (e.g., the distribution in
FIG. 1 ) may probably change after the flash memory has been subject to a predetermined number of program/erase cycles or/and a predetermined data retention time has elapsed. For example, as shown inFIG. 2 (in which only two states are concerned and shown for illustrative purpose), the initial distribution represented by the (dotted)curve 20 with reference voltage V4 may be suffered from retention issue after a long time not going through program/erase cycle, and therefore drifted downward to a shifted distribution represented by the (solid)curve 22 with a new reference voltage V4′. Errors probably incur if the reference voltage V4 of theinitial distribution 20 is still used (while the new reference voltage V4′ is unknown) to read data from the flash memory. - For the reason that conventional MLC flash memory could probably result in read errors due to cycle/retention issue, a need has arisen to propose some novel schemes to obtain proper reference voltages for reading data from the MLC flash memory.
- In view of the foregoing, it is an object of the present invention to provide system and method for effectively and economically finding proper reference voltages for reading data from a MLC flash memory without errors due to cycle/retention issue.
- According to one embodiment, an initial threshold voltage distribution is provided that includes data pairs <N,V>, each including normalized number N of cells of the flash memory and corresponding threshold voltage V in the initial threshold voltage distribution. The normalized number N1 of the cells corresponding to a given threshold voltage V1 in a shifted threshold voltage distribution to be determined is obtained. Subsequently, search to find, in the initial threshold voltage distribution, a threshold voltage V2 which has a corresponding normalized number of cells approximate to the number N1. Finally, initial reference voltage or voltages of the initial threshold voltage distribution are shifted with an amount approximate to difference between the threshold voltage V2 and the given threshold voltage V1, thereby resulting in new reference voltage or voltages for reading the data from the MLC flash memory.
- According to another embodiment, total number N of cells of the flash memory above a reference threshold voltage of a reference state in an initial threshold voltage distribution is provided. Subsequently, search to find a threshold voltage Va corresponding to a state above which totals number of the cells is approximate to the total number N. Finally, initial reference voltage or voltages of the initial threshold voltage distribution are shifted with an amount approximate to difference between the threshold voltage Va and the reference threshold voltage, thereby resulting in new reference voltage or voltages for reading the data from the MLC flash memory.
-
FIG. 1 shows a common distribution of the threshold voltage for a typical MLC flash memory; -
FIG. 2 shows that a portion of the threshold voltage distribution inFIG. 1 changes after the flash memory has been subject to program/erase cycles or/and data retention time has elapsed; -
FIG. 3A shows an exemplary threshold voltage distribution of a MLC flash memory, illustrating the aspect according to the first embodiment of the present invention; -
FIG. 3B shows a flow diagram corresponding to the aspect of the first embodiment ofFIG. 3A ; -
FIG. 4A shows an exemplary threshold voltage distribution of a MLC flash memory, illustrating the aspect according to the second embodiment of the present invention; -
FIG. 4B shows a flow diagram corresponding to the aspect of the second embodiment ofFIG. 4A ; and -
FIG. 5 shows a block diagram illustrating a memory system for adaptively finding proper reference voltages for reading data from a MLC flash memory according to one embodiment of the present invention. -
FIG. 3A shows an exemplary threshold voltage distribution of a multi-level cell (MLC) flash memory, illustrating the aspect according to the first embodiment of the present invention.FIG. 3B shows a flow diagram corresponding to the aspect of the first embodiment. InFIG. 3A , (solid)curve 300 represents the initial distribution of the threshold voltage of a state of the flash memory. Another (dotted)curve 302 inFIG. 3A represents a threshold voltage distribution after the flash memory has been subject to a predetermined number of program/erase cycles or/and a predetermined data retention time has elapsed. Thecurve 302 is supposed to shift or drift downward (e.g., leftward in the figure) as shown due to the cycle/retention issue after a long time not going through program/erase cycle. It is noted that only one state is shown while other states are omitted in the figure for brevity. - In the embodiment, after the flash memory is requested by a read command (the step 31), we can get from the flash memory the number of cells (for example, N1) at a threshold voltage (for example, V1). What we can also get from the flash memory is the number of cells of a state or states from a spare area of the flash memory which we store at program phase. If the number of cells at that state is N, the value N1 is normalized (in the step 32) to be N1/N.
- Subsequently, in the
step 33, normalized <N,V> data of the initial distribution represented by thecurve 300 are retrieved. The known normalized <N,V> data is stored beforehand, for example, in a look up table (LUT), where N represents the normalized number of cells and V represents the corresponding threshold voltage. - Next, in the
step 34, compare the normalized <N1,V1> of the shifteddistribution 302 with the normalized <N,V> of theinitial distribution 300 in order to find the threshold voltage V2 in the initialthreshold voltage distribution 300 which has a corresponding normalized number N2 of cells approximate the value N1. The search for finding the threshold voltage V2 may utilize a conventional search method. In the embodiment, the term “approximate” may mean that the number to be searched is within a predetermined range of a target value N1, and may include the case in which the searched number is equal to the target value. - Finally, in the
step 35, a new reference voltage for reading data from the MLC flash memory due to the cycle/retention issue is obtained by shifting the original reference voltage downward with the amount of the difference of V2 and V1 (i.e., V2−V1). In one exemplary embodiment, all reference voltages are shifted with the same amount V2−V1. In another exemplary embodiment, different reference voltage is shifted with different amount. For example, if the calculated shift amount for the reference voltage V7 is 1 volts, then the shift amount for the reference voltage V6 may be 0.9 volts, and the shift amount for the reference voltage V5 may be 0.8 volts. -
FIG. 4A shows an exemplary threshold voltage distribution of a MLC flash memory, illustrating the aspect according to the second embodiment of the present invention.FIG. 4B shows a flow diagram corresponding to the aspect of the second embodiment. InFIG. 4A , (solid) curves 400 represent the initial distribution of the threshold voltage of the states of the flash memory. Another (dotted) curves 402 in theFIG. 4A represent a threshold voltage distribution after the flash memory has been subject to a predetermined number of program/erase cycles or/and a predetermined data retention time has elapsed. Thecurves 402 are supposed to shift or drift downward (e.g., leftward in the figure) as shown due to the cycle/retention issue after a long time not going through program/erase cycle. - In the embodiment, after the flash memory is requested by a read command (the step 41), the total number Na of the cells above a specific state (e.g., above the threshold voltage Va) of the shifted
distribution 402 is obtained (the step 42). Subsequently, search to find a reference state (such as the program verify voltage Vpv inFIG. 4A ), above which the total number N of cells is equal or approximate to Na. The search for finding the reference state may be implemented, in the embodiment, by performing the steps 43-48. Specifically speaking, in thestep 43, the first (i.e., i=0) word line voltage is set, followed by retrieving known <N,V> data, in which N represents the total number of cells above certain state (the step 44). - Afterwards, the number N is compared with the number Na (the step 45). If the difference (N−Na) is not less than a predetermined value m (such as the acceptable error tolerance) and the maximum world line voltage has not been reached (the step 46), next word line voltage is then set (the step 47). The steps 44-45 iterate until the difference (N−Na) is less than the predetermined m (the step 45) or the maximum world line voltage has been reached (the step 46). At that time, a new reference voltage for reading data from the MLC flash memory due to the cycle/retention issue is obtained by shifting the original reference voltage downward with the amount of the difference of Vpv and Va (i.e., Vpv−Va). In one exemplary embodiment, all reference voltages are shifted with the same amount Vpv-Va. In another exemplary embodiment, different reference voltage is shifted with different amount.
- According to the first embodiment (FIG. 3A/B) and the second embodiment (FIG. 4A/B) discussed above, the embodiments of the present invention associate a first threshold voltage (e.g., V2 in
FIG. 3A or Vpv inFIG. 4A ) in the initial distribution with a second threshold voltage (e.g., V1 inFIG. 3A or Va inFIG. 4A ) in a shifted distribution to be determined, such that the information (e.g., the normalized number N1 of cells inFIG. 3A or the total number Na of cells above a state inFIG. 4A ) corresponding to the second threshold voltage is approximate to the information corresponding to the first threshold voltage. The difference between the first threshold voltage and the second threshold voltage is then determined and subsequently utilized to correct the reference voltage(s) of the initial threshold voltage distribution due to the cycle/retention issue. It is worthy of noting that, as the effort to obtain the information and determine the difference concerns only basic calculations, the embodiments of the present invention may not only effectively but also economically find proper reference voltages for reading data from a MLC flash memory without much latency. -
FIG. 5 shows a block diagram illustrating amemory system 5 for adaptively finding proper reference voltages for reading data from a MLC flash memory according to one embodiment of the present invention. Thememory system 5 may be adapted to the first embodiment (Fir. 3A/B) or the second embodiment (FIG. 4A/B). Thememory system 5 includes aflash memory 50 and amemory controller 52. Data may be written (programmed) to or read from theflash memory 50 from/to a host (not shown) through thememory controller 52. Regarding theflash memory 50, the data being written to or read from the memory cells (not shown) of theflash memory 50 may be temporarily stored in apage buffer 500, and operation and timing of theflash memory 50 is managed bycontrol logic 502. Regarding thememory controller 52, adata buffer 520 is used for temporarily storing data and for interfacing with theflash memory 50, andcontrol logic 522 is used for managing the operation and timing of thememory controller 52. - The
memory controller 52 further includes a data pair <N,V>generator 524 that generates the normalized number N1 of cells corresponding to respective threshold voltage V1 (in the first embodiment) or generates the total number Na of cells above respective state (in the second embodiment). Thememory controller 52 also includes a referencevoltage decision device 528 that associates a first threshold voltage (e.g., V2 inFIG. 3A or Vpv inFIG. 4A ) in the initial distribution with a second threshold voltage (e.g., V1 inFIG. 3A or Va inFIG. 4A ) in a shifted distribution to be determined, such that the information (e.g., the normalized number N1 of cells inFIG. 3A or the total number Na of cells above a state inFIG. 4A ) corresponding to the first threshold voltage is approximate to the information corresponding to the second threshold voltage. The difference between the first threshold voltage and the second threshold voltage is then determined by the referencevoltage decision device 528. In addition, what might also be required, for the first embodiment only, is a look up table (LUT) 526 for pre-storing the known normalized <N,V> data of the initial distribution. The amount approximate to the difference is subsequently utilized to correct the initial reference voltage(s) due to the cycle/retention issue. It is appreciated by those skilled in the pertinent technical field that the blocks (500-528) of thememory system 5 may be implemented using hardware technique (such as circuit) or software technique (such as program run on a microcontroller) or their combination. - Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
Claims (16)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/464,240 US7848152B1 (en) | 2009-05-12 | 2009-05-12 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
TW098119665A TWI370459B (en) | 2009-05-12 | 2009-06-12 | Method and system for adaptively finding reference voltages for reading data from a mlc flash memory |
US12/915,573 US8355285B2 (en) | 2009-05-12 | 2010-10-29 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/464,240 US7848152B1 (en) | 2009-05-12 | 2009-05-12 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/915,573 Division US8355285B2 (en) | 2009-05-12 | 2010-10-29 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
Publications (2)
Publication Number | Publication Date |
---|---|
US20100290282A1 true US20100290282A1 (en) | 2010-11-18 |
US7848152B1 US7848152B1 (en) | 2010-12-07 |
Family
ID=43068396
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/464,240 Active 2029-07-09 US7848152B1 (en) | 2009-05-12 | 2009-05-12 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
US12/915,573 Active 2030-01-20 US8355285B2 (en) | 2009-05-12 | 2010-10-29 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/915,573 Active 2030-01-20 US8355285B2 (en) | 2009-05-12 | 2010-10-29 | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory |
Country Status (2)
Country | Link |
---|---|
US (2) | US7848152B1 (en) |
TW (1) | TWI370459B (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20120084503A1 (en) * | 2010-10-01 | 2012-04-05 | Canon Kabushiki Kaisha | Disk control apparatus, disk control method, and storage medium storing disk control program |
GB2498875A (en) * | 2012-01-30 | 2013-07-31 | HGST Netherlands BV | Data read of a drift tolerant moving baseline data encoded multi-level memory cell (MLC) |
US8792272B2 (en) | 2012-01-30 | 2014-07-29 | HGST Netherlands B.V. | Implementing enhanced data partial-erase for multi-level cell (MLC) memory using threshold voltage-drift or resistance drift tolerant moving baseline memory data encoding |
US8861276B2 (en) | 2011-06-21 | 2014-10-14 | Samsung Electronics Co., Ltd. | Nonvolatile memory device, memory system comprising same, and method of operating same |
Families Citing this family (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8351258B1 (en) | 2010-01-22 | 2013-01-08 | Marvell International Ltd. | Adapting read reference voltage in flash memory device |
US8531888B2 (en) * | 2010-07-07 | 2013-09-10 | Marvell World Trade Ltd. | Determining optimal reference voltages for progressive reads in flash memory systems |
US20130006896A1 (en) * | 2011-06-28 | 2013-01-03 | Seagate Technology Llc | Training Datasets for Memory Devices |
US8913437B2 (en) * | 2011-12-15 | 2014-12-16 | Marvell World Trade Ltd. | Inter-cell interference cancellation |
US8797805B2 (en) * | 2011-12-22 | 2014-08-05 | Micron Technology, Inc. | Methods and apparatuses for determining threshold voltage shift |
US8848453B2 (en) | 2012-08-31 | 2014-09-30 | Micron Technology, Inc. | Inferring threshold voltage distributions associated with memory cells via interpolation |
US8984369B2 (en) | 2012-11-21 | 2015-03-17 | Micron Technology, Inc. | Shaping codes for memory |
US9076545B2 (en) | 2013-01-17 | 2015-07-07 | Sandisk Tecnologies Inc. | Dynamic adjustment of read voltage levels based on memory cell threshold voltage distribution |
TWI515743B (en) | 2013-11-20 | 2016-01-01 | 旺宏電子股份有限公司 | Method, electronic device and controller for recovering array of memory cells |
KR102174030B1 (en) | 2014-05-13 | 2020-11-05 | 삼성전자주식회사 | Storage device including nonvolatile memory device and read method thereof |
KR102238592B1 (en) | 2014-08-08 | 2021-04-09 | 삼성전자주식회사 | Method of setting default read voltage of non-volatile memory device and method of reading data of non-volatile memory device |
US9852799B2 (en) | 2014-11-19 | 2017-12-26 | Sandisk Technologies Llc | Configuration parameter management for non-volatile data storage |
KR102397016B1 (en) | 2014-11-24 | 2022-05-13 | 삼성전자주식회사 | Operatiing method of nonvolatile memory system |
KR102284658B1 (en) | 2015-03-19 | 2021-08-02 | 삼성전자 주식회사 | Non-volatile memory device, Memory system including the same, and Method of operating the same |
CN111105835B (en) * | 2019-12-03 | 2022-03-18 | 长江存储科技有限责任公司 | Method for determining read reference voltage of memory |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080181010A1 (en) * | 2007-01-25 | 2008-07-31 | Macronix International Co., Ltd. | Flash memory and method for determining logic states thereof |
US20080205136A1 (en) * | 2007-02-22 | 2008-08-28 | Hynix Semiconductor Inc. | Read method of memory device |
US20080263266A1 (en) * | 2007-04-23 | 2008-10-23 | Sandisk Il Ltd. | Adaptive dynamic reading of flash memories |
US20090290426A1 (en) * | 2008-05-20 | 2009-11-26 | Violante Moschiano | Charge loss compensation during programming of a memory device |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008111058A2 (en) | 2007-03-12 | 2008-09-18 | Anobit Technologies Ltd. | Adaptive estimation of memory cell read thresholds |
-
2009
- 2009-05-12 US US12/464,240 patent/US7848152B1/en active Active
- 2009-06-12 TW TW098119665A patent/TWI370459B/en active
-
2010
- 2010-10-29 US US12/915,573 patent/US8355285B2/en active Active
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080181010A1 (en) * | 2007-01-25 | 2008-07-31 | Macronix International Co., Ltd. | Flash memory and method for determining logic states thereof |
US20080205136A1 (en) * | 2007-02-22 | 2008-08-28 | Hynix Semiconductor Inc. | Read method of memory device |
US20080263266A1 (en) * | 2007-04-23 | 2008-10-23 | Sandisk Il Ltd. | Adaptive dynamic reading of flash memories |
US20090290426A1 (en) * | 2008-05-20 | 2009-11-26 | Violante Moschiano | Charge loss compensation during programming of a memory device |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20120084503A1 (en) * | 2010-10-01 | 2012-04-05 | Canon Kabushiki Kaisha | Disk control apparatus, disk control method, and storage medium storing disk control program |
US8861276B2 (en) | 2011-06-21 | 2014-10-14 | Samsung Electronics Co., Ltd. | Nonvolatile memory device, memory system comprising same, and method of operating same |
GB2498875A (en) * | 2012-01-30 | 2013-07-31 | HGST Netherlands BV | Data read of a drift tolerant moving baseline data encoded multi-level memory cell (MLC) |
US8792272B2 (en) | 2012-01-30 | 2014-07-29 | HGST Netherlands B.V. | Implementing enhanced data partial-erase for multi-level cell (MLC) memory using threshold voltage-drift or resistance drift tolerant moving baseline memory data encoding |
US9208871B2 (en) | 2012-01-30 | 2015-12-08 | HGST Netherlands B.V. | Implementing enhanced data read for multi-level cell (MLC) memory using threshold voltage-drift or resistance drift tolerant moving baseline memory data encoding |
Also Published As
Publication number | Publication date |
---|---|
TWI370459B (en) | 2012-08-11 |
TW201040982A (en) | 2010-11-16 |
US20110038209A1 (en) | 2011-02-17 |
US7848152B1 (en) | 2010-12-07 |
US8355285B2 (en) | 2013-01-15 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7848152B1 (en) | Method and system for adaptively finding reference voltages for reading data from a MLC flash memory | |
US8072805B2 (en) | Method and system of finding a read voltage for a flash memory | |
US11150808B2 (en) | Flash memory system | |
US8130544B2 (en) | Method of reducing bit error rate for a flash memory | |
US8472280B2 (en) | Alternate page by page programming scheme | |
US7643348B2 (en) | Predictive programming in non-volatile memory | |
CN103069494B (en) | Natural threshold voltage distribution compression in nonvolatile memory | |
US7602652B2 (en) | Systems for programming differently sized margins and sensing with compensations at select states for improved read operations in non-volatile memory | |
US8107287B2 (en) | Method of programming nonvolatile memory device | |
CN101079322B (en) | Multi-bit memory device and memory system | |
US8464135B2 (en) | Adaptive flash interface | |
US7782667B2 (en) | Method of operating a flash memory device | |
US20080253193A1 (en) | Non-Volatile Memory with Predictive Programming | |
US9384839B2 (en) | Write sequence providing write abort protection | |
US20100034021A1 (en) | Method of controlling operation of flash memory device | |
US9053011B2 (en) | Selective protection of lower page data during upper page write | |
US8923071B2 (en) | Method of programming a multi-bit per cell non-volatile memory | |
US8279676B2 (en) | Method of operating nonvolatile memory device | |
US7907445B2 (en) | Method and system for obtaining a reference block for a MLC flash memory |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: SKYMEDI CORPORATION, TAIWAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HUANG, CHIEN-FU;CHOU, MING-HUNG;HUANG, HAN-LUNG;AND OTHERS;REEL/FRAME:022672/0656 Effective date: 20090415 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
FPAY | Fee payment |
Year of fee payment: 4 |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 8TH YR, SMALL ENTITY (ORIGINAL EVENT CODE: M2552) Year of fee payment: 8 |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 12TH YR, SMALL ENTITY (ORIGINAL EVENT CODE: M2553); ENTITY STATUS OF PATENT OWNER: SMALL ENTITY Year of fee payment: 12 |