Patents by Inventor Abhijith Prakash
Abhijith Prakash 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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Publication number: 20250104774Abstract: Embodiments disclosed herein are directed to performing a single-side gate-induced drain leakage (GIDL) erase operation. Control circuitry may be configured to perform a single-side GIDL erase operation on a memory block in which a selected sub-block is erased while an unselected sub-block is not erased. During the single-side GIDL erase operation, the control circuitry may be configured to apply a first unselect bias voltage to a first set of word lines of the unselected sub-block, where the first set of word lines is associated with a first word line zone and the first word line zone is associated with an unselect bias voltage, and apply a second unselect bias voltage to a second set of word lines of the unselected sub-block, where the second set of word lines is associated with a second word line zone and the second word line zone is associated with another unselect bias voltage.Type: ApplicationFiled: September 21, 2023Publication date: March 27, 2025Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Publication number: 20250061948Abstract: The memory device includes circuitry which is configured to sense threshold voltages of the memory cells of a selected word line of the plurality of word lines in a sensing operation. During the sensing operation, the circuitry, in a first sensing process, senses the memory cells of the selected word line using both a fast read technique and a positive sensing technique. The circuitry also determines a fail bit count and compares the fail bit count to a threshold. In response to the fail bit count being less than or equal to the threshold, the circuitry completes the sensing operation. In response to the fail bit count exceeding the threshold, then the circuitry performs a second sensing process to sense threshold voltages of the memory cells of the selected word line using a relatively slower read technique.Type: ApplicationFiled: August 15, 2023Publication date: February 20, 2025Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang, Wei Cao
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Patent number: 12230333Abstract: Systems and methods for bit line modulation to compensate for cell source variation are disclosed. For example, a method for reading data from non-volatile storage comprising determining a first bit line level based on a first programmed data state that is being sensed and determining a second bit line level based on a second programmed data state that is being sensed. As another example, a storage device comprising a first bit line driver configured to generate a first bit line level for a first set of bit lines corresponding to a first set of memory strings based on a first cell source level associated with the first set of memory strings a second bit line driver configured to generate a second bit line level for a second set of bit lines corresponding to a second set of memory strings based on a second cell source level associated with the second set of memory strings.Type: GrantFiled: September 28, 2022Date of Patent: February 18, 2025Assignee: SanDisk Technologies LLCInventors: Anirudh Amarnath, Aravind Suresh, Abhijith Prakash
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Publication number: 20250037783Abstract: Multiple non-volatile memory dies are tested to identify word lines that have a first reliability and word lines that have a second reliability. Word lines that have the first reliability are designated to store data at a first number of bits per memory cell. Word lines that have the second reliability are designated to store data at a second number of bits per memory cell. The second number of bits per memory cell include more bits per memory cell than the first number of bits per memory cell.Type: ApplicationFiled: July 29, 2023Publication date: January 30, 2025Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Jiahui Yuan, Xiang Yang
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Publication number: 20250006285Abstract: Technology is disclosed herein for detecting evolved bad blocks in three-dimensional NAND. The test may include a drain side erase that includes applying an erase voltage from the bit lines and a source side erase that includes applying an erase voltage from the source line(s). If the source side erase performed worse than the drain side erase this may indicate a defect near the source side of the block. For example, the source side erase may fail but the drain side erase may pass. As another example the source side erase may take at least a pre-determined number of additional erase pulses to pass than the drain side erase. If the block is found as having a defect the entire block could be marked bad or the defective region could be identified such that the defective region is no longer used.Type: ApplicationFiled: July 27, 2023Publication date: January 2, 2025Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Parth Amin, Xiang Yang
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Publication number: 20240427662Abstract: A memory device includes a memory block including a plurality of sub-blocks each including a plurality of memory cells and control circuitry configured to perform single-side erase operations on the memory block in a sub-block mode in which a selected sub-block of the plurality of sub-blocks in the memory block is erased while unselected sub-blocks of the plurality of sub-blocks in the memory block are not erased and selectively perform data scrubbing and relocation operations on the plurality of sub-blocks of the memory block. To perform a data scrubbing and relocation operation, the control circuitry is configured to determine whether to perform the data scrubbing and relocation operation on a first sub-block based on a position of the first sub-block relative to an erase side of the memory block and selectively perform the data scrubbing and relocation operation on the first sub-block in response to the determination.Type: ApplicationFiled: August 10, 2023Publication date: December 26, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Publication number: 20240395328Abstract: The nonvolatile memory includes a plurality of nonvolatile memory cells configured to store multiple data states; a word line connected to a control gate of at least one of the plurality of non-volatile memory cells; a control gate line to supply a control gate signal; a word line switch connected between the word line and the control gate line to control the potential applied to the word line from the control gate line; and a memory controller circuit. The memory controller circuit is configured to control a word line potential on the word line and a control gate potential on the control gate line and to control a state of the control gate. The memory controller circuit, when the nonvolatile memory transitions to a not-on state, is further configured to turn off the word line switch and to charge the control gate line to a charged potential.Type: ApplicationFiled: July 31, 2024Publication date: November 28, 2024Applicant: SanDisk Technologies LLCInventors: Abhijith Prakash, Anubhav Khandelwal
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Publication number: 20240386969Abstract: The memory device includes sensing circuitry that senses data in the memory cells of a selected word line. If the memory device is in the first operating mode, the sensing circuitry senses the selected word line with a first sensing process that includes applying a first voltage to a source side of at least one NAND string and ramping at least one voltage applied to the memory block to a target voltage over a first duration. If the memory device is in the second operating mode, the sensing circuitry senses the selected word line with a second sensing process that includes applying a second voltage to the source side of at least one NAND string and ramping the at least one voltage applied to the memory block to the target voltage over a second duration that is greater than or equal to the first duration.Type: ApplicationFiled: July 31, 2023Publication date: November 21, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang, Wei Cao
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Patent number: 12148478Abstract: A non-volatile memory system comprises a plurality of non-volatile memory cells divided into three or more tiers. The memory cells can be programmed, erased and read. In order to achieve uniform erase speed for the three or more tiers, the erase process comprises applying a larger voltage bias to control gates of non-volatile memory cells in the outer tiers than the voltage bias applied to control gates of non-volatile memory cells in one or more inner tiers.Type: GrantFiled: September 26, 2022Date of Patent: November 19, 2024Assignee: SanDisk Technologies LLCInventors: Xiang Yang, Masaaki Higashitani, Abhijith Prakash, Dengtao Zhao
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Publication number: 20240363168Abstract: The memory device includes a chip with at least one voltage pump and a plurality of planes. The planes have arrays of memory cells that can be programmed and erased. At least some of the planes are at different distances from the at least one voltage pump. The memory device further includes control circuitry that is configured to program and erase the memory cells. The control circuitry is further configured to supply at least one voltage to a selected plane of the plurality of planes during a programming operation or an erase pulse and adjust the at least one voltage that is supplied to the selected plane by a parameter that is determined based on a distance between the selected plane and the at least one voltage pump.Type: ApplicationFiled: August 4, 2023Publication date: October 31, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Publication number: 20240363177Abstract: A memory apparatus and method of operation are provided. The apparatus includes drain-side select gate transistors for coupling to a drain-side of memory holes of and configured to retain a transistor threshold voltage. The memory holes are arranged in rows comprising strings. The rows include semi-circle rows comprising the memory holes being partially cut by a slit half etch and full circle rows comprising the memory holes not cut. A control means is coupled to the drain-side select gate transistors of the memory holes and is configured to determine whether a downshift recovery trigger event has occurred in a plurality of memory operations. In response to determining the downshift recovery trigger event has occurred, the control means programs the transistor threshold voltage of the drain-side select gate transistors of the memory holes in at least one of the semi-circle rows to a target transistor threshold voltage.Type: ApplicationFiled: July 26, 2023Publication date: October 31, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Publication number: 20240304251Abstract: The memory device includes a quick pass write (QPW) voltage source and a transistor that can control the supply of a first QPW bias voltage to a plurality of bit lines. Control circuitry programs the memory cells of a selected word line in a plurality of program loops. For each memory cell in the selected word line, the control circuitry determines if the memory cell is within either a first or a second QPW zone. If the memory cell is in the second QPW zone, the control circuitry connects the QPW voltage source to the bit line that is in communication with that memory cell to supply the first QPW bias voltage to the bit line. In response to a determination that the memory cell is in the first QPW zone, the control circuitry controls the transistor to supply an average second QPW bias voltage to the bit line.Type: ApplicationFiled: July 18, 2023Publication date: September 12, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Publication number: 20240304262Abstract: The memory device an array of memory cells arranged in a word lines and a one common source line (CELSRC) driver. Control circuitry is configured to program the memory cells of a selected word line in a plurality of program loops. During the program loops, the control circuitry sets a voltage of the CELSRC driver to approximately zero Volts, applies a verify voltage to the selected word line, applies a pass voltage to unselected word lines, and applies a bit line voltage to a bit line that is coupled to a memory cell to be sensed. During at least one early program loop for a given data state, the control circuitry increases the bit line voltage or increases the pass voltage. The control circuitry is further configured to reduce the bit line voltage or the pass voltage for the verify operations in at least one subsequent program loop.Type: ApplicationFiled: July 25, 2023Publication date: September 12, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Patent number: 12087363Abstract: The nonvolatile memory includes a plurality of nonvolatile memory cells configured to store multiple data states; a word line connected to a control gate of at least one of the plurality of non-volatile memory cells; a control gate line to supply a control gate signal; a word line switch connected between the word line and the control gate line to control the potential applied to the word line from the control gate line; and a memory controller circuit. The memory controller circuit is configured to control a word line potential on the word line and a control gate potential on the control gate line and to control a state of the control gate. The memory controller circuit, when the nonvolatile memory transitions to a not-on state, is further configured to turn off the word line switch and to charge the control gate line to a charged potential.Type: GrantFiled: February 14, 2023Date of Patent: September 10, 2024Assignee: SanDisk Technologies LLCInventors: Abhijith Prakash, Anubhav Khandelwal
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Publication number: 20240290402Abstract: The memory device includes a memory block with memory cells arranged in word lines and control circuitry that is configured to program the memory cells in a selected word line to respective programmed data states in program loops, which each include verify operations. The control circuitry is further configured to lock out any of the memory cells in the selected word line memory cell from subsequent program pulses and verify operations in response to that memory cell passing verify for its respective programmed data state. For a selected programmed data state, the control circuitry is further configured to re-verify all of the memory cells in the selected word line that are being programmed to the selected programmed data state and release all memory cells that were locked out but fail re-verify in order to allow any memory cells that mistakenly passed verify to be programmed further.Type: ApplicationFiled: July 19, 2023Publication date: August 29, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Patent number: 12046305Abstract: A memory apparatus and method of operation are provided. The apparatus includes memory cells connected to word lines including a dummy word line and other data word lines. The memory cells are disposed in memory holes and configured to retain a threshold voltage. A control means is coupled to the word lines and the memory holes and is configured to determine whether one of the word lines being programmed in a program operation is a particular one of the word lines adjacent the dummy word line needing a dummy positioning operation. The control means is also configured to program the memory cells connected to the dummy word line to adjust the threshold voltage to a predetermined position threshold voltage in the dummy positioning operation in response to determining the one of the plurality of word lines being programmed in the program operation is the particular one of the word lines.Type: GrantFiled: February 4, 2022Date of Patent: July 23, 2024Assignee: SanDisk Technologies LLCInventors: Xiang Yang, Abhijith Prakash
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Publication number: 20240212767Abstract: The memory device includes a memory block with an array of memory cells arranged word lines. The memory device also includes control circuitry that is configured to program final data into a selected word line in a multi-pass programming operation that includes a first pass and a second pass. In the first pass, the control circuitry is configured to program the memory cells of the selected word line to foggy data and program parity data in the memory device. The parity data includes three possible data states. Prior to the second pass, the control circuitry is configured to read the foggy data and the parity data and reconstruct the final data from the foggy data and the parity data. In the second pass, the control circuitry is configured to program the memory cells of the selected word line from the foggy data to the final data.Type: ApplicationFiled: July 24, 2023Publication date: June 27, 2024Applicant: SanDisk Technologies LLCInventors: Abhijith Prakash, Xiang Yang
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Publication number: 20240185928Abstract: A method for performing a read operation of a fully programmed non-volatile memory that, initially, was partially programmed, the method comprising: selecting a word line within an initially programmed portion; applying a read to the selected word line, determining a first “optimal” read verify voltage level for each program state; once fully programmed, applying a read to the selected word line, determining a second “optimal” read verify voltage level for each program state; for each program state, determining a difference between the first “optimal” read verify voltage level and the second “optimal” read verify voltage level, the difference defining a supplemental offset value; determining an “optimal” read verify voltage level for each program state by applying the supplemental offset value in conjunction with an initial offset value defined in a pre-calibrated “lookup” table; and applying a read to each word line according to each determined “optimal” read verify voltage level.Type: ApplicationFiled: July 7, 2023Publication date: June 6, 2024Applicant: Western Digital Technologies, Inc.Inventors: Abhijith Prakash, Xiang Yang
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Patent number: 11972808Abstract: A memory apparatus and method of operation are provided. The apparatus includes memory cells connected to word lines and disposed in memory holes organized in rows grouped in strings and configured to retain a threshold voltage. The memory cells are connected in series between a drain-side select gate transistor on a drain-side of each of the memory holes and a source-side select gate transistor on a source-side of each of the memory holes. A control means determines whether a downshift recovery trigger event has occurred in memory operations. In response to determining the downshift recovery trigger event has occurred, the control means inserts at least one of a predetermined idle time in the memory operations and a recovery pulse of a negative voltage to the drain-side select gate transistor of the memory holes of the strings for a predetermined pulse period of time during one of the memory operations.Type: GrantFiled: February 8, 2022Date of Patent: April 30, 2024Assignee: SanDisk Technologies, LLCInventors: Abhijith Prakash, Xiang Yang
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Patent number: 11972818Abstract: A memory apparatus and method of operation are provided. The apparatus includes memory cells each connected to word lines. The memory cells are disposed in strings and configured to retain a threshold voltage corresponding to data states. A control means is configured to apply verification pulses of program verify voltages each associated with one of the data states to selected ones of the word lines to determine whether the memory cells connected thereto have the threshold voltage above each of the program verify voltages targeted for each of the memory cells during a program-verify portion of a program operation. The control means is also configured to trim the program verify voltages for each of the data states for a grouping of the memory cells based on quantities of the memory cells having the threshold voltage crossing over between the data states in crossovers in a verify level trimming process.Type: GrantFiled: June 15, 2022Date of Patent: April 30, 2024Assignee: SanDisk Technologies, LLCInventors: Abhijith Prakash, Xiang Yang