Patents by Inventor Hock C. So

Hock C. So 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: 6330185
    Abstract: A multi-level non-volatile memory includes one or more arrays of memory cells including storage cells and dummy cells. The memory observes or measures write operations that write dummy values to the dummy cells and from the observations or measurements selects parameters such as programming voltages or the duration of program cycles. The selection of parameters optimizes write precision within the available access time of a high bandwidth memory. Accessing dummy cells also allows the memory to reach a steady state before writing or reading of data begins. In particular, multiple pipelines sequentially start write operations, and writing of data begins when an equilibrium number of pipelines are performing write operations. Similarly, multiple read operation start before the reading of data for actual use. The stabilization is particularly critical when the pipelines share a power source.
    Type: Grant
    Filed: January 23, 2001
    Date of Patent: December 11, 2001
    Assignee: Multi Level Memory Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 6307776
    Abstract: A multibit-per-cell non-volatile memory divides the suitable threshold voltages of memory cells into ranges corresponding to allowed states for storage of data and ranges corresponding to forbidden zones indicating a data error. A read process in accordance automatically checks whether a threshold voltage is in a forbidden zone. In an alternative embodiment, a refresh process includes reprogramming the threshold voltage into an allowed state. In the case of a flash memory, a refresh reads a sector of the memory and saves corrected data from the sector in a buffer or another sector. The corrected data from the buffer or other sector can be written back in the original sector, or the corrected data can be left in the other sector with addresses of the original sector being mapped to the other sector.
    Type: Grant
    Filed: October 6, 2000
    Date of Patent: October 23, 2001
    Assignee: Sandisk Corporation
    Inventors: Hock C. So, Sau C. Wong
  • Patent number: 6278633
    Abstract: A multi-level non-volatile memory includes one or more arrays of memory cells including storage cells and dummy cells. The memory observes or measures write operations that write dummy values to the dummy cells and from the observations or measurements selects parameters such as programming voltages or the duration of program cycles. The selection of parameters optimizes write precision within the available access time of a high bandwidth memory. Accessing dummy cells also allows the memory to reach a steady state before writing or reading of data begins. In particular, multiple pipelines sequentially start write operations, and writing of data begins when an equilibrium number of pipelines are performing write operations. Similarly, multiple read operation start before the reading of data for actual use. The stabilization is particularly critical when the pipelines share a power source.
    Type: Grant
    Filed: November 5, 1999
    Date of Patent: August 21, 2001
    Assignee: Multi Level Memory Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 6208542
    Abstract: An integrated circuit stores analog or digital information, or both, in memory cells (416). The memory cells provide analog or multilevel storage. Analog information is provided through an analog signal input (405), and digital information is provided through a digital signal input (407). A scheme for storing digital information is consistent with the scheme used to store analog information. Data is retrieved from the memory cells, and output to the analog or digital signal output (454, 463) depending on the type of data. A digital reference generator reference generator (425) generates various analog equivalent voltages for the digital signal input.
    Type: Grant
    Filed: June 2, 1999
    Date of Patent: March 27, 2001
    Assignee: SanDisk Corporation
    Inventors: Cheng-Yuan Michael Wang, Andreas M. Haeberli, Carl W. Werner, Sau C. Wong, Hock C. So, Leon Sea Jiunn Wong
  • Patent number: 6184726
    Abstract: Level shifter circuits are used to configure analog or multilevel memory cells. A level shifter circuit generates an output voltage that is above the input voltage by an offset voltage value. The magnitude of this offset voltage or the relationship between the input and output voltages of the level shifter is adjustable or programmably selectable. Adjustments can be made after the integrated circuits is fabricated and packaged. Adjustments are made by configuring bits of data in the integrated circuit to indicate the offset voltage or other parameters. These configuration bits are implemented using latches, flip-flops, registers, memory cells, or other storage circuits.
    Type: Grant
    Filed: June 29, 1999
    Date of Patent: February 6, 2001
    Assignee: SanDisk Corporation
    Inventors: Andreas M. Haeberli, Carl W. Werner, Cheng-Yuan Michael Wang, Hock C. So, Leon Sea Jiunn Wong, Sau C. Wong
  • Patent number: 6185119
    Abstract: An integrated circuit memory is capable of storing analog information without the need for A/D conversion. Samples of a analog signal input are stored in nonvolatile memory cells. The integrated circuit is also capable of storing digital information in digital form. The sampling rate at which the analog signal input is sampled is user selectable. An internal signal path of the integrated circuit memory is differential, which enhances the precision with which the analog signal is stored in the memory cells.
    Type: Grant
    Filed: June 29, 1999
    Date of Patent: February 6, 2001
    Assignee: SanDisk Corporation
    Inventors: Andreas M. Haeberli, Carl W. Werner, Hock C. So, Sau C. Wong, Cheng-Yuan Michael Wang, Leon Sea Jiunn Wong
  • Patent number: 6151246
    Abstract: A multibit-per-cell non-volatile memory divides the suitable threshold voltages of memory cells into ranges corresponding to allowed states for storage of data and ranges corresponding to forbidden zones indicating a data error. A read process in accordance automatically checks whether a threshold voltage is in a forbidden zone. In an alternative embodiment, a refresh process includes reprogramming the threshold voltage into an allowed state. In the case of a flash memory, a refresh reads a sector of the memory and saves corrected data from the sector in a buffer or another sector. The corrected data from the buffer or other sector can be written back in the original sector, or the corrected data can be left in the other sector with addresses of the original sector being mapped to the other sector.
    Type: Grant
    Filed: November 25, 1998
    Date of Patent: November 21, 2000
    Assignee: SanDisk Corporation
    Inventors: Hock C. So, Sau C. Wong
  • Patent number: 5969986
    Abstract: A memory architecture for a non-volatile analog or multiple-bits-per-cell memory includes multiple separate memory arrays and multiple read/write pipelines. The multiple read/write pipelines share a read circuit and/or a write circuit to reduce the circuit area of each pipeline and the circuit area of the memory as a whole. In one embodiment, a shared write circuit generates a programming voltage that changes with an input signal representing values to be written to the memory. Each pipeline includes a sample-and-hold circuit that samples the programming voltage when the pipeline begins a write operation. The write circuit can additionally generate a verify voltage that a second sample-and-hold circuit in each pipeline samples when starting a write operation.
    Type: Grant
    Filed: June 23, 1998
    Date of Patent: October 19, 1999
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5949716
    Abstract: Continuous recording in a flash memory uses a look-ahead erase process that includes simultaneously writing data to a first sector in a first array while preparing (erasing and/or partially programming) a second sector in a second array. The second sector is ready for writing when a last datum fills the first sector and is immediately available for writing while a third sector is prepared. The look-ahead erase keeps preparing sectors so that writing can continue without interruptions for erase processes. Embodiments of the invention include integrated circuit memories having two or more memory arrays, each having a plurality of independently erasable sectors. Each time a sector is filled the write process switches to a sector in another array.
    Type: Grant
    Filed: April 16, 1997
    Date of Patent: September 7, 1999
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5943283
    Abstract: A semiconductor memory includes a memory array and an address scrambler. The address scrambler maps sequential input addresses to non-sequential physical addresses for the memory array. In one embodiment, the address scramble includes circuitry that implements a one-to-one function mapping of the logical addresses to physical addresses. Alternatively, the address scrambler includes a pseudo-random series generator that generates a pseudo-random series for the physical addresses. In either case, consecutive memory accesses that would logically correspond to a single row or column are scattered among multiple rows and columns to diminish the length of a gap in a data sequence that would otherwise occur as a result of a defective row or column. For flash memory, the mapping can be restricted so that logical addresses for a sector map to physical address for the same or another sector.
    Type: Grant
    Filed: December 5, 1997
    Date of Patent: August 24, 1999
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5923585
    Abstract: A non-volatile memory includes an array of memory cells that is partitioned into sectors with sources of memory cells in each sector coupled together but electrically isolated from sources of memory cells in other sectors. Each sector includes one or more rows of memory cells, and sources of memory cells in each row are coupled together by a source-line. During programming of a selected memory cell, a bias circuit grounds a source-line in the sector containing the selected memory cell and applies a bias voltage to the source-lines in the other sectors. The bias voltage reduces program disturb of memory cells that are connected to the same bit-line as the selected memory cell. The bias circuit is coupled to address decode circuitry that indicates which source-line should be grounded.
    Type: Grant
    Filed: January 10, 1997
    Date of Patent: July 13, 1999
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5909449
    Abstract: A multilevel non-volatile memory divides the suitable threshold voltages of memory cells into ranges corresponding to allowed states for storage of data and ranges corresponding to forbidden zones indicating a data error. A read process in accordance automatically checks whether a threshold voltage is in a forbidden zone. In alternative embodiment, a refresh process includes reprogramming the threshold voltage into an allowed state or in the case of a flash memory, reading a sector of the memory, saving data from the sector in a buffer, erasing the sector, and rewriting the data from the buffer back in the sector. Refresh process for the non-volatile memory can be perform in response to detecting a threshold voltage in a forbidden zone, as part of a power-up procedure for the memory, or periodically with a period on the order of days, weeks, or months.
    Type: Grant
    Filed: September 8, 1997
    Date of Patent: June 1, 1999
    Assignee: Invox Technology
    Inventors: Hock C. So, Sau C. Wong
  • Patent number: 5909387
    Abstract: A semiconductor memory stores multiple messages such as multiple sound clips and includes storage cells dedicated to storage of samples that constitute the messages and EOM cells dedicated to storage of marks identifying boundaries of the messages. In one embodiment, a set of the EOM cells are together in a row of an array, and each such EOM cell is associated with storage cells in the same column of the array. Each EOM cell is erased together with associated storage cells. To avoid overerase of EOM cells, a write process for a storage cell asserts a write pulse to the associated EOM cell. Write pulses resulting from writing of multiple storage cells associated with an EOM cell, change a threshold voltage of the EOM cell from the erased state to a partially programmed state. The EOM cell associated with a boundary of a message can be programmed to a state that differs from the partially programmed state.
    Type: Grant
    Filed: June 2, 1997
    Date of Patent: June 1, 1999
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5896340
    Abstract: A memory architecture divides memory cells of a memory into multiple memory arrays where each memory array has local row and column lines that are directly coupled to memory cells in the memory array and electrically isolated from other arrays. Continuous global row and column lines cross the memory arrays. The memory additionally includes global decoders that apply operating voltages to the global lines corresponding to a selected memory cell being access. Local decoders decode bits from the address signal to select an array containing the selected memory cell and connect the global lines to the selected memory array. Other memory arrays are disconnected from the global lines to avoid disturbance that would result from the operating voltage being applied to unselected memory cells. Alternative, embodiments include a memory including a row of memory arrays, or a column of memory arrays, or multiple rows and multiple columns of memory arrays.
    Type: Grant
    Filed: July 7, 1997
    Date of Patent: April 20, 1999
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5818757
    Abstract: Applying a bias voltage to unselected word-lines reduces program disturb of the threshold voltages of unselected memory cells during a write to a non-volatile memory. Applying the bias voltage only to memory cells which have already been written with threshold voltages higher than a minimum value and not to erased (or virgin) memory cells allows the bias voltage to be higher without creating currents through unselected memory cells. Data such as a series of samples representing a continuous analog signal can be recorded by writing to sequential addresses to fill one row in an array with data before writing to the next row. Bias flag circuits in a row decoder of the memory indicate which rows are filled with data and therefore which word-lines should have the bias voltage applied during a write.
    Type: Grant
    Filed: July 22, 1996
    Date of Patent: October 6, 1998
    Assignee: Invox Technology
    Inventors: Hock C. So, Sau C. Wong
  • Patent number: 5815425
    Abstract: A non-volatile memory stores both analog and digital information in an array, and has digital and analog read and write circuits and dual I/O interfaces which allow input and output signals in digital or analog form. A user selects the input signal, output signal, and data storage formats. Each selection can be digital or analog format. On-chip analog-to-digital and digital-to-analog converters allow conversion of signals from one format into another. Analog signals can be read or written serially, and one embodiment includes an address counter and an internal oscillator for generating sequential addresses. An output amplifier for driving a speaker and an input amplifier for a microphone allow stored sounds to be directly recorded and reproduced. A real-time recording method in accordance with an embodiment of the invention writes digital samples to the memory using a fast digital write circuit while data is being acquired.
    Type: Grant
    Filed: April 30, 1997
    Date of Patent: September 29, 1998
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5801980
    Abstract: A non-volatile memory stores both analog and digital information in an array, and has digital and analog read and write circuits and dual I/O interfaces which allow input and output signals in digital or analog form. A user selects the input signal, output signal, and data storage formats. Each selection can be digital or analog format. On-chip analog-to-digital and digital-to-analog converters allow conversion of signals from one format into another. Analog signals can be read or written serially, and one embodiment includes an address counter and an internal oscillator for generating sequential addresses. An output amplifier for driving a speaker and an input amplifier for a microphone allow stored sounds to be directly recorded and reproduced.
    Type: Grant
    Filed: May 1, 1997
    Date of Patent: September 1, 1998
    Assignee: Invox Technology
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5751635
    Abstract: Circuits and processes write and read analog signals in non-volatile memory cells such as EPROM and flash EPROM cells. One read circuit process determines a memory cell's threshold voltage by slowly ramps the control gate voltage of a memory cell being read and senses when the memory cell conducts. Another read circuit determines the threshold voltage of a memory cell using a source follower read process and a ramping circuit which slowly increases the source voltage. Still another read circuit includes a cascoding device connectable to a memory cell, bias circuit for biasing the memory cell in its linear region, and a load which carries a current that mirrors the current through the memory cell wherein the threshold voltage of the memory cell is determined from a voltage across the load. Read circuits disclosed can be used with analog memory cells, binary memory cells, multi-level digital memory cells, and other applications which require precise reading of threshold voltages.
    Type: Grant
    Filed: January 11, 1996
    Date of Patent: May 12, 1998
    Assignee: inVoice Technology, Inc.
    Inventors: Sau C. Wong, Hock C. So
  • Patent number: 5748534
    Abstract: To read the threshold voltage of a transistor such as a floating gate transistor in an analog or multi-level memory cell, the transistor is connected in a feedback loop which contains a differential amplifier having an output terminal and an input terminal respectively connected to the gate and a node (source or drain) of the transistor. A reference voltage is asserted to a second input terminal of the differential amplifier. A load provides a current which charges the node, and the differential amplifier adjusts the gate voltage of the memory cell to an equilibrium value where current through the transistor is equal to current through the reference cell. The equilibrium value of the gate voltage depends on and indicates the threshold voltage of the transistor. In one embodiment of the invention, the load is a current source which mirrors a current through a reference cell that is structurally identical to the transistor, and the drain of the reference cell provides the reference voltage to the amplifier.
    Type: Grant
    Filed: March 26, 1996
    Date of Patent: May 5, 1998
    Assignee: Invox Technology
    Inventors: Frank M. Dunlap, Hock C. So, Sau C. Wong
  • Patent number: 5748533
    Abstract: A read circuit includes a driver which changes a gate voltage of a memory cell and a sense circuit which identifies when the memory cell trips. The driver searches for the threshold voltage of the memory cell using stages which ramp up gate voltage and stages which ramp down the gate voltage. Each stage ends when the sense circuit senses that the memory cell trips, i.e. begins or stops conducting. Initial stages of the search have high ramp rates so that the gate voltage reaches the threshold voltage. These initial stages can give inaccurate threshold voltage readings because high ramp rates change the gate voltage during the period between the transistor tripping and sensing the trip. Later stages ramp the gate voltage slowly to provide an accurate threshold voltage reading. The low ramp rate of the last stage provides accuracy, and the high ramp rate of the initial stages reduces read time. To further reduce read time, the search process can begin at a median voltage for possible threshold voltages.
    Type: Grant
    Filed: March 26, 1996
    Date of Patent: May 5, 1998
    Assignee: inVoice Technology, Inc.
    Inventors: Frank M Dunlap, Hock C. So, Sau C. Wong