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).
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Patent number: 8111551Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: GrantFiled: May 2, 2011Date of Patent: February 7, 2012Assignees: Kabushiki Kaisha Toshiba, Sandisk CorporationInventors: Tomoharu Tanaka, Koichi Kawai, Khandker N Quader
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Publication number: 20110205794Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: ApplicationFiled: May 2, 2011Publication date: August 25, 2011Inventors: Tomoharu Tanaka, Koichi Kawai, Khandker N. Quader
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Patent number: 7952925Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: GrantFiled: July 29, 2010Date of Patent: May 31, 2011Assignees: Kabushiki Kaisha Toshiba, SanDisk CorporationInventors: Tomoharu Tanaka, Koichi Kawai, Khandker N Quader
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Publication number: 20100296339Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: ApplicationFiled: July 29, 2010Publication date: November 25, 2010Inventors: Tomoharu Tanaka, Koichi Kawai, Khandker N. Quader
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Patent number: 7787296Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: GrantFiled: April 23, 2008Date of Patent: August 31, 2010Assignees: Kabushiki Kaisha Toshiba, SanDisk CorporationInventors: Tomoharu Tanaka, Koichi Kawai, Khandker N Quader
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Patent number: 7468915Abstract: 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: GrantFiled: October 4, 2006Date of Patent: December 23, 2008Assignee: SanDisk CorporationInventors: Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader
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Patent number: 7420846Abstract: 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: GrantFiled: April 8, 2004Date of Patent: September 2, 2008Assignee: SanDisk CorporationInventors: Jian Chen, Khandker N. Quader
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Publication number: 20080205143Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: ApplicationFiled: April 23, 2008Publication date: August 28, 2008Inventors: Tomoharu TANAKA, Koichi Kawai, Khandker N. Quader
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Patent number: 7394704Abstract: 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: GrantFiled: November 30, 2005Date of Patent: July 1, 2008Assignees: Kabushiki Kaisha Toshiba, Sandisk CorporationInventors: Tomoharu Tanaka, Khandker N. Quader, Hiroyuki Dohmae, Atsushi Inoue, Takeaki Sato
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Patent number: 7379346Abstract: A non-volatile memory and method for its operation that can reduce the amount of disturb in non-selected cells during an erase process are presented. For a set of storage elements formed over a common well structure, all word-lines are initially charged with the same high voltage erase signal that charges the well to insure there is no net voltage difference between the well and word-lines. The selected word-lines are then discharged to ground while the non-selected word-lines and the well are maintained at the high voltage. This can be accomplished without increasing any pitch area circuit or adding new wires in the memory array, and at minimal additional peripheral area. Advantages include less potential erase disturb in the non-selected storage elements and a tighter erase distribution for the selected elements.Type: GrantFiled: September 8, 2005Date of Patent: May 27, 2008Assignee: SanDisk CorporationInventors: Khandker N. Quader, Raul-Adrian Cernea
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Patent number: 7376010Abstract: A nonvolatile semiconductor memory device includes a memory cell array constituted by a plurality of memory blocks, an interface, a write circuit, and a read circuit. A protect flag is written in the memory block. The readout protect flag can be output to an external device through the interface. When a write command is input from the interface, the write circuit executes the write command when the protect flag in the selected memory block has a first value and does not execute the write command when the protect flag has a second value.Type: GrantFiled: March 24, 2006Date of Patent: May 20, 2008Assignees: Kabushiki Kaisha Toshiba, SanDisk CorporationInventors: Tomoharu Tanaka, Koichi Kawai, Khandker N. Quader
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Patent number: 7224613Abstract: 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: GrantFiled: August 16, 2005Date of Patent: May 29, 2007Assignees: SanDisk Corporation, Kabushiki Kaisha ToshibaInventors: Jian Chen, Tomoharu Tanaka, Yupin Fong, Khandker N. Quader
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Patent number: 7145804Abstract: 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: GrantFiled: September 28, 2005Date of Patent: December 5, 2006Assignee: SanDisk CorporationInventors: Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader
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Patent number: 7095654Abstract: 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: GrantFiled: September 9, 2005Date of Patent: August 22, 2006Assignee: SanDisk CorporationInventors: Khandker N. Quader, Khanh T. Nguyen, Feng Pan, Long C. Pham, Alexander K. Mak
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Patent number: 7061798Abstract: 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: GrantFiled: October 15, 2004Date of Patent: June 13, 2006Assignees: SanDisk Corporation, Kabushiki Kaisha ToshibaInventors: Jian Chen, Tomoharu Tanaka, Yupin Fong, Khandker N. Quader
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Patent number: 7046548Abstract: 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: GrantFiled: February 9, 2005Date of Patent: May 16, 2006Assignee: SanDisk CorporationInventors: Raul-Adrian Cernea, Khandker N. Quader, Yan Li, Jian Chen, Yupin Fong
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Patent number: 6990018Abstract: A non-volatile semiconductor memory device including 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: GrantFiled: April 14, 2004Date of Patent: January 24, 2006Assignees: Kabushiki Kaisha Toshiba, SanDisk CorporationInventors: Tomoharu Tanaka, Khandker N. Quader, Hiroyuki Dohmae, Atsushi Inoue, Takeaki Sato
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Patent number: 6977844Abstract: 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: GrantFiled: February 8, 2005Date of Patent: December 20, 2005Assignee: SanDisk CorporationInventors: Daniel C. Guterman, George Samachisa, Brian Murphy, Chi-Ming Wang, Khandker N. Quader
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Patent number: 6967872Abstract: 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: GrantFiled: December 18, 2001Date of Patent: November 22, 2005Assignee: SanDisk CorporationInventors: Khandker N. Quader, Khanh T. Nguyen, Feng Pan, Long C. Pham, Alexander K. Mak
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Patent number: 6958936Abstract: The present invention presents a non-volatile memory and method for its operation that can reduce the amount of disturb in non-selected cells during an erase process. For a set of storage elements formed over a common well structure, all word-lines are initially charged with the same high voltage erase signal that charges the well to insure there is no net voltage difference between the well and word-lines. The selected word-lines are then discharged to ground while the non-selected word-lines and the well are maintained at the high voltage. According to another aspect of the present invention, this can be accomplished without increasing any pitch area circuit or adding new wires in the memory array, and at minimal additional peripheral area. Advantages include less potential erase disturb in the non-selected storage elements and a tighter erase distribution for the selected elements.Type: GrantFiled: September 25, 2003Date of Patent: October 25, 2005Assignee: SanDisk CorporationInventors: Khandker N. Quader, Raul-Adrian Cernea