Patents by Inventor Khandker N. Quader

Khandker N. Quader has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6944068
    Abstract: A multi-level non-volatile memory cell programming/lockout method and system are provided. The programming/lockout method and system advantageously prevent memory cells that charge faster than other memory cells from being over-programmed.
    Type: Grant
    Filed: March 24, 2004
    Date of Patent: September 13, 2005
    Assignee: SanDisk Corporation
    Inventors: Khandker N. Quader, Khanh T. Nguyen, Feng Pan, Long C. Pham, Alexander K. Mak
  • Patent number: 6888752
    Abstract: In a non-volatile memory, the displacement current generated in non-selected word lines that results when the voltage levels on an array's bit lines are changed can result in disturbs. Techniques for reducing these currents are presented. In a first aspect, the number of cells being simultaneously programmed on a word line is reduced. In a non-volatile memory where an array of memory cells is composed of a number of units, and the units are combined into planes that share common word lines, the simultaneous programming of units within the same plane is avoided. Multiple units may be programmed in parallel, but these are arranged to be in separate planes. This is done by selecting the number of units to be programmed in parallel and their order such that all the units programmed together are from distinct planes, by comparing the units to be programmed to see if any are from the same plane, or a combination of these.
    Type: Grant
    Filed: July 1, 2003
    Date of Patent: May 3, 2005
    Assignee: SanDisk Corporation
    Inventors: John S. Mangan, Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader
  • Patent number: 6870768
    Abstract: Techniques of reducing erroneous readings of the apparent charge levels stored in a number of rows of memory cells on account of capacitive coupling between the cells. All pages of a first row are programmed with a first pass, followed by programming all pages of a second adjacent row with a first pass, after which the first row is programmed with a second pass, and then all pages of a third row are programmed with a first pass, followed by returning to program the second row with a second pass, and so on, in a back-and-forth manner across the rows of an array. This minimizes the effect on the apparent charge stored on rows of memory cells that can occur by later writing data into adjacent rows of memory cells.
    Type: Grant
    Filed: August 20, 2004
    Date of Patent: March 22, 2005
    Assignee: SanDisk Corporation
    Inventors: Raul-Adrian Cernea, Khandker N. Quader, Yan Li, Jian Chen, Yupin Fong
  • Patent number: 6839281
    Abstract: In a non-volatile memory, the read parameter used to distinguish the data states characterized by a negative threshold voltage from the data states characterized by a positive threshold voltage is compensated for the memory's operating conditions, rather than being hardwired to ground. In an exemplary embodiment, the read parameter for the data state with the lowest threshold value above ground is temperature compensated to reflect the shifts of the storage element populations on either side of the read parameter. According to another aspect, an erase process is presented that can take advantage the operating condition compensated sensing parameter. As the sensing parameter is no longer fixed at a value corresponding to 0 volts, instead shifling according to operating conditions, a sufficient margin is provided for the various erase verify levels even at lowered operating voltages.
    Type: Grant
    Filed: April 14, 2003
    Date of Patent: January 4, 2005
    Inventors: Jian Chen, Khandker N. Quader
  • Publication number: 20040257874
    Abstract: Disclosed is a non-volatile semiconductor memory device comprising a plurality of non-volatile semiconductor memory cells, an interface making data exchange with an external device to write/read data with respect to the non-volatile semiconductor memory cells, and a control circuit for controlling the non-volatile semiconductor memory cells, wherein the interface and the control circuit include a first read mode initialized via a first bootstrap to read data from the non-volatile semiconductor memory cells for continuously outputting (N+M)-byte (N is the n-th power of 2, n is positive integers) data via the interface, and a second read mode initialized via a second bootstrap to read data from the non-volatile semiconductor memory cells for continuously outputting K-byte (K is the k-th power of 2, k is positive integers) data via the interface.
    Type: Application
    Filed: April 14, 2004
    Publication date: December 23, 2004
    Inventors: Tomoharu Tanaka, Khandker N. Quader, Hiroyuki Dohmae, Atsushi Inoue, Takeaki Sato
  • Patent number: 6807095
    Abstract: A non-volatile memory system having an array of memory cells with at least one storage element each is operated with a plurality of storage level ranges per storage element. A flash electrically erasable and programmable read only memory (EEPROM) is an example, wherein the storage elements are electrically floating gates. The memory is operated to minimize the effect of charge coupled between adjacent floating gates, by programming some cells a second time after adjacent cells have been programmed. The second programming step also compacts a distribution of charge levels within at least some of the programming states. This increases the separation between states and/or allows more states to be included within a given storage window. An implementation that is described is for a NAND type of flash EEPROM.
    Type: Grant
    Filed: December 18, 2002
    Date of Patent: October 19, 2004
    Assignees: SanDisk Corporation, Kabushiki Kaisha Toshiba
    Inventors: Jian Chen, Tomoharu Tanaka, Yupin Fong, Khandker N. Quader
  • Publication number: 20040202023
    Abstract: In a non-volatile memory, the read parameter used to distinguish the data states characterized by a negative threshold voltage from the data states characterized by a positive threshold voltage is compensated for the memory's operating conditions, rather than being hardwired to ground. In an exemplary embodiment, the read parameter for the data state with the lowest threshold value above ground is temperature compensated to reflect the shifts of the storage element populations on either side of the read parameter. According to another aspect, an erase process is presented that can take advantage the operating condition compensated sensing parameter. As the sensing parameter is no longer fixed at a value corresponding to 0 volts, instead shifting according to operating conditions, a sufficient margin is provided for the various erase verify levels even at lowered operating voltages.
    Type: Application
    Filed: April 14, 2003
    Publication date: October 14, 2004
    Inventors: Jian Chen, Khandker N. Quader
  • Publication number: 20040179404
    Abstract: A multi-level non-volatile memory cell programming/lockout method and system are provided. The programming/lockout method and system advantageously prevent memory cells that charge faster than other memory cells from being over-programmed.
    Type: Application
    Filed: March 24, 2004
    Publication date: September 16, 2004
    Inventors: Khandker N. Quader, Khanh T. Nguyen, Feng Pan, Long C. Pham, Alexander K. Mak
  • Patent number: 6781877
    Abstract: Techniques of reducing erroneous readings of the apparent charge levels stored in a number of rows of memory cells on account of capacitive coupling between the cells. All pages of a first row are programmed with a first pass, followed by programming all pages of a second adjacent row with a first pass, after which the first row is programmed with a second pass, and then all pages of a third row are programmed with a first pass, followed by returning to program the second row with a second pass, and so on, in a back-and-forth manner across the rows of an array. This minimizes the effect on the apparent charge stored on rows of memory cells that can occur by later writing data into adjacent rows of memory cells.
    Type: Grant
    Filed: September 6, 2002
    Date of Patent: August 24, 2004
    Assignee: SanDisk Corporation
    Inventors: Raul-Adrian Cernea, Khandker N. Quader, Yan Li, Jian Chen, Yupin Fong
  • Patent number: 6717851
    Abstract: In a non-volatile memory, the displacement current generated in non-selected word lines that results when the voltage levels on an array's bit lines are changed can result in disturbs. Techniques for reducing these currents are presented. In a first aspect, the number of cells being simultaneously programmed on a word line is reduced. In a non-volatile memory where an array of memory cells is composed of a number of units, and the units are combined into planes that share common word lines, the simultaneous programming of units within the same plane is avoided. Multiple units may be programmed in parallel, but these are arranged to be in separate planes. This is done by selecting the number of units to be programmed in parallel and their order such that all the units programmed together are from distinct planes, by comparing the units to be programmed to see if any are from the same plane, or a combination of these.
    Type: Grant
    Filed: January 10, 2001
    Date of Patent: April 6, 2004
    Assignee: SanDisk Corporation
    Inventors: John S. Mangan, Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader
  • Publication number: 20040047182
    Abstract: Techniques of reducing erroneous readings of the apparent charge levels stored in a number of rows of memory cells on account of capacitive coupling between the cells. All pages of a first row are programmed with a first pass, followed by programming all pages of a second adjacent row with a first pass, after which the first row is programmed with a second pass, and then all pages of a third row are programmed with a first pass, followed by returning to program the second row with a second pass, and so on, in a back-and-forth manner across the rows of an array. This minimizes the effect on the apparent charge stored on rows of memory cells that can occur by later writing data into adjacent rows of memory cells.
    Type: Application
    Filed: September 6, 2002
    Publication date: March 11, 2004
    Inventors: Raul-Adrian Cernea, Khandker N. Quader, Yan Li, Jian Chen, Yupin Fong
  • Patent number: 6696880
    Abstract: The invention utilizes a boost-strap method to improve switch operation in a design that is particularly advantageous for supplying high voltages within a low voltage design. A native NMOS transistor, a PMOS transistor, and a capacitor are connected in series between the high voltage source and the output, where the gate of the native NMOS is connect to the output. In an initialization phase, the plate of the capacitor connected to the output is precharged by receiving the input signal while the other plate of the capacitor is held near ground. In a subsequent enable phase, the native NMOS and PMOS transistors are turned on and the high voltage is supplied to the output.
    Type: Grant
    Filed: November 9, 2001
    Date of Patent: February 24, 2004
    Assignee: SanDisk Corporation
    Inventors: Feng Pan, Khandker N. Quader
  • Publication number: 20040027865
    Abstract: In a non-volatile memory, the displacement current generated in non-selected word lines that results when the voltage levels on an array's bit lines are changed can result in disturbs. Techniques for reducing these currents are presented. In a first aspect, the number of cells being simultaneously programmed on a word line is reduced. In a non-volatile memory where an array of memory cells is composed of a number of units, and the units are combined into planes that share common word lines, the simultaneous programming of units within the same plane is avoided. Multiple units may be programmed in parallel, but these are arranged to be in separate planes. This is done by selecting the number of units to be programmed in parallel and their order such that all the units programmed together are from distinct planes, by comparing the units to be programmed to see if any are from the same plane, or a combination of these.
    Type: Application
    Filed: July 1, 2003
    Publication date: February 12, 2004
    Inventors: John S. Mangan, Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader
  • Publication number: 20030128586
    Abstract: A non-volatile memory system having an array of memory cells with at least one storage element each is operated with a plurality of storage level ranges per storage element. A flash electrically erasable and programmable read only memory (EEPROM) is an example, wherein the storage elements are electrically floating gates. The memory is operated to minimize the effect of charge coupled between adjacent floating gates, by programming some cells a second time after adjacent cells have been programmed. The second programming step also compacts a distribution of charge levels within at least some of the programming states. This increases the separation between states and/or allows more states to be included within a given storage window. An implementation that is described is for a NAND type of flash EEPROM.
    Type: Application
    Filed: December 18, 2002
    Publication date: July 10, 2003
    Inventors: Jian Chen, Tomoharu Tanaka, Yupin Fong, Khandker N. Quader
  • Publication number: 20030112663
    Abstract: A multi-level non-volatile memory cell programming/lockout method and system are provided. The programming/lockout method and system advantageously prevent memory cells that charge faster than other memory cells from being over-programmed.
    Type: Application
    Filed: December 18, 2001
    Publication date: June 19, 2003
    Inventors: Khandker N. Quader, Khanh T. Nguyen, Feng Pan, Long C. Pham, Alexander K. Mak
  • Publication number: 20030090311
    Abstract: The invention utilizes a boost-strap method to improve switch operation in a design that is particularly advantageous for supplying high voltages within a low voltage design. A native NMOS transistor, a PMOS transistor, and a capacitor are connected in series between the high voltage source and the output, where the gate of the native NMOS is connect to the output. In an initialization phase, the plate of the capacitor connected to the output is precharged by receiving the input signal while the other plate of the capacitor is held near ground. In a subsequent enable phase, the native NMOS and PMOS transistors are turned on and the high voltage is supplied to the output.
    Type: Application
    Filed: November 9, 2001
    Publication date: May 15, 2003
    Inventors: Feng Pan, Khandker N. Quader
  • Patent number: 6522580
    Abstract: A non-volatile memory system having an array of memory cells with at least one storage element each is operated with a plurality of storage level ranges per storage element. A flash electrically erasable and programmable read only memory (EEPROM) is an example, wherein the storage elements are electrically floating gates. The memory is operated to minimize the effect of charge coupled between adjacent floating gates, by programming some cells a second time after adjacent cells have been programmed. The second programming step also compacts a distribution of charge levels within at least some of the programming states. This increases the separation between states and/or allows more states to be included within a given storage window. An implementation that is described is for a NAND type of flash EEPROM.
    Type: Grant
    Filed: June 27, 2001
    Date of Patent: February 18, 2003
    Assignee: SanDisk Corporation
    Inventors: Jian Chen, Tomoharu Tanaka, Yupin Fong, Khandker N. Quader
  • Publication number: 20030002348
    Abstract: A non-volatile memory system having an array of memory cells with at least one storage element each is operated with a plurality of storage level ranges per storage element. A flash electrically erasable and programmable read only memory (EEPROM) is an example, wherein the storage elements are electrically floating gates. The memory is operated to minimize the effect of charge coupled between adjacent floating gates, by programming some cells a second time after adjacent cells have been programmed. The second programming step also compacts a distribution of charge levels within at least some of the programming states. This increases the separation between states and/or allows more states to be included within a given storage window. An implementation that is described is for a NAND type of flash EEPROM.
    Type: Application
    Filed: June 27, 2001
    Publication date: January 2, 2003
    Applicant: SanDisk Corporation
    Inventors: Jian Chen, Tomoharu Tanaka, Yupin Fong, Khandker N. Quader
  • Patent number: 6396757
    Abstract: A multiple output current mirror of improved accuracy suitable for use in a multi-level memory or analog applications is described. A reference current is mirrored in number of branches to produce replicas of the original current without degrading the original current. Both the mirrored transistor, through which the original current flows, and the mirroring transistors, which provide the replicated currents in each of the branches, are subdivided into a number of separate transistors. The effective channel width of a corresponding original transistor is shared among the transistors forming its subdivision. These subdivided elements are then physically arranged into a number partial current mirrors whose outputs are combined to form the total current mirror.
    Type: Grant
    Filed: July 24, 2001
    Date of Patent: May 28, 2002
    Assignee: SanDisk Corporation
    Inventors: Khandker N. Quader, Sharon Y. Huynh
  • Publication number: 20020051383
    Abstract: In a non-volatile memory, the displacement current generated in non-selected word lines that results when the voltage levels on an array's bit lines are changed can result in disturbs. Techniques for reducing these currents are presented. In a first aspect, the number of cells being simultaneously programmed on a word line is reduced. In a non-volatile memory where an array of memory cells is composed of a number of units, and the units are combined into planes that share common word lines, the simultaneous programming of units within the same plane is avoided. Multiple units may be programmed in parallel, but these are arranged to be in separate planes. This is done by selecting the number of units to be programmed in parallel and their order such that all the units programmed together are from distinct planes, by comparing the units to be programmed to see if any are from the same plane, or a combination of these.
    Type: Application
    Filed: January 10, 2001
    Publication date: May 2, 2002
    Inventors: John S. Mangan, Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader