Patents by Inventor K. Subramanian

K. Subramanian 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).

  • Publication number: 20040008536
    Abstract: A MRAM toggle type memory cell is read by first providing a first signal representative of the initial state to a sense amplifier (1300, 1500). A resistance of the cell is temporarily changed by altering a magnetic polarization of the free layer of the cell. A second signal responsive to altering the resistance of the MRAM cell is provided to the sense amplifier (1300, 1500). The first signal is compared to the second signal to determine the state of the MRAM cell.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 15, 2004
    Inventors: Bradley J. Garni, Thomas W. Andre, Joseph J. Nahas, Chitra K. Subramanian
  • Publication number: 20040001352
    Abstract: A magnetoresistive random access memory is operated in a toggle fashion so that its logic state is flipped from its current state to the alternate state when written. This provides for a more consistent and reliable programming because the magnetic transitional energy states during the toggle operation are stable. In a write situation, however, this does mean that the state of the cell must be read and compared to the desired state of the cell before the cell is flipped. If the cell is already in the desired logic state, then it should not be written. This read time penalty before writing is reduced by beginning the write process while reading and then aborting the write step if the cell is already in the desired state. The write can actually begin on the cell and be aborted without adversely effecting the state of the cell.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 1, 2004
    Inventors: Joseph J. Nahas, Thomas W. Andre, Chitra K. Subramanian, Brad J. Garni
  • Publication number: 20040001358
    Abstract: A magnetoresistive random access memory (MRAM) has separate read and write paths. This reduces the peripheral circuitry by not requiring switching between read and write functions on a particular line. By having the paths dedicated to either read signals or write signals, the voltage levels can be optimized for these functions. The select transistors, which are part of only the read function, may be of the low-voltage type because they do not have to receive the relatively higher voltages of the write circuitry. Similarly, the write voltages do not have to be degraded to accommodate the lower-voltage type transistors. The size of the overall memory is kept efficiently small while improving performance. The memory cells are grouped so that adjacent to groups are coupled to a common global bit line which reduces the space required for providing the capacitance-reducing group approach to memory cell selection.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 1, 2004
    Inventors: Joseph J. Nahas, Thomas W. Andre, Chitra K. Subramanian, Bradley J. Garni, Mark A. Durlam
  • Publication number: 20040001361
    Abstract: A memory provides a sensing scheme that maintains impedance balance between the route that the data takes to the sense amplifier and the route the reference or references take to the sense amplifier. Each sub-array of the memory has an adjacent column decoder that couples data to a data line that is also adjacent to the sub-array and may be considered part of the column decoder. The data for the selected sub-array is routed to the sense amplifier via its adjacent data line. The reference that is part of the selected sub-array is coupled to the data line of a non-selected sub-array. Thus the reference, which in the case of a MRAM type memory is preferably in close proximity to the location of the selected data, traverses a route to the sense amplifier that is impedance balanced with respect to the route taken by the data.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 1, 2004
    Inventors: Chitra K. Subramanian, Brad J. Garni, Joseph J. Nahas, Halbert S. Lin, Thomas W. Andre
  • Publication number: 20040001351
    Abstract: A magnetoresistive random access memory (MRAM) has separate read and write paths. Switchable current mirrors, each having multiple series-connected stages, receive a common reference current. A timing circuit provides control signals to word and bit decoders and to the switchable current mirrors to selectively complete current paths through a predetermined write word line and a predetermined write bit line. Bit lines are connected together at a common end, and word lines are connected together at a common end. By precharging a common rail having multiple write bit lines connected together, the write noise immunity is improved and current spikes are minimized. Groups of bit lines may be connected via a metal option to adjust a transition time of a programming current.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 1, 2004
    Inventors: Chitra K. Subramanian, Thomas W. Andre, Joseph J. Nahas
  • Publication number: 20040001383
    Abstract: A sense amplifier (1300, 1500) is provided for sensing the state of a toggling type magnetoresistive random access memory (MRAM) cell without using a reference. The sense amplifier (1300, 1500) employs a sample-and-hold circuit (1336, 1508) combined with a current-to-voltage converter (1301, 1501), gain circuit (1303), and cross-coupled latch (1305, 1503) to sense the state of a bit. The sense amplifier (1300, 1500), first senses and holds a first state of the cell. The cell is toggled to a second state. Then, the sense amplifier (1300, 1500) compares the first state to the second state to determine the first state of a toggling type memory cell.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 1, 2004
    Inventors: Bradley J. Garni, Mark F. Deherrera, Mark A. Durlam, Bradley N. Engel, Thomas W. Andre, Joseph J. Nahas, Chitra K. Subramanian
  • Publication number: 20040001360
    Abstract: A magnetoresistive random access memory (MRAM) has separate read and write paths. Switchable current mirrors, each having multiple series-connected stages, receive a common reference current. A timing circuit provides control signals to word and bit decoders and to the switchable current mirrors to selectively complete current paths through a predetermined write word line and a predetermined write bit line. Bit lines are connected together at a common end, and word lines are connected together at a common end. By precharging a common rail having multiple write bit lines connected together, the write noise immunity is improved and current spikes are minimized. Groups of bit lines may be connected via a metal option to adjust a transition time of a programming current.
    Type: Application
    Filed: June 28, 2002
    Publication date: January 1, 2004
    Inventors: Chitra K. Subramanian, Thomas W. Andre, Joseph J. Nahas
  • Patent number: 6667899
    Abstract: A magnetic memory (400) is programmed by selectively conducting current in opposite directions in both word and bit lines to reduce electromigration effects in word lines and bit lines. Various criteria, such as a data value being programmed and a previous current direction are used to determine the direction of the write currents used in the word and bit lines during programming.
    Type: Grant
    Filed: March 27, 2003
    Date of Patent: December 23, 2003
    Assignee: Motorola, Inc.
    Inventors: Chitra K. Subramanian, Thomas W. Andre, Joseph J. Nahas
  • Patent number: 6657889
    Abstract: A magnetoresistive random access memory (MRAM) has separate read and write paths. Switchable current mirrors, each having multiple series-connected stages, receive a common reference current. A timing circuit provides control signals to word and bit decoders and to the switchable current mirrors to selectively complete current paths through a predetermined write word line and a predetermined write bit line. Bit lines are connected together at a common end, and word lines are connected together at a common end. By precharging a common rail having multiple write bit lines connected together, the write noise immunity is improved and current spikes are minimized. Groups of bit lines may be connected via a metal option to adjust a transition time of a programming current.
    Type: Grant
    Filed: June 28, 2002
    Date of Patent: December 2, 2003
    Assignee: Motorola, Inc.
    Inventors: Chitra K. Subramanian, Thomas W. Andre, Bradley J. Garni, Halbert S. Lin, Joseph J. Nahas
  • Patent number: 6621729
    Abstract: A sense amplifier (10) develops internally a midpoint reference current from two reference bits. The midpoint reference current is used to sense the state of a memory bit having at least two distinct resistance states (H and L) by determining whether the sense memory bit develops a larger or smaller current. The midpoint reference current is developed within a single sense amplifier. Predetermined bias voltages are developed from each of a data bit cell, a reference cell programmed to a high state and a reference cell programmed to a low state. Currents are developed from the bias voltages and summed to create the midpoint reference current. A current differential amplifier senses whether the bit input has a high or low resistive state and outputs a voltage indicative of the sensed memory state.
    Type: Grant
    Filed: June 28, 2002
    Date of Patent: September 16, 2003
    Assignee: Motorola, Inc.
    Inventors: Bradley J. Garni, Chitra K. Subramanian, Joseph J. Nahas, Thomas W. Andre
  • Patent number: 6600690
    Abstract: In a memory, a sensing system detects bit states using one data and two reference inputs, to sense a difference in conductance of a selected memory bit cell and a midpoint reference conductance. Reference conductance is generated as the average conductance of a memory cell in the high conductance state and a memory cell in the low conductance state. The data input is coupled to the selected memory bit cell. The two reference inputs are respectively coupled to memory cells in high and low conductance memory states. The sense amplifiers use either current biasing or voltage biasing to apply a sensing voltage within a predetermined voltage range across the bit cells. Capacitance coupled to complementary outputs of the sense amplifiers is balanced by the circuit designs. In one form, the two reference inputs are internally connected. One of several gain stages amplifies the sense amplifier output without injecting parasitic errors.
    Type: Grant
    Filed: June 28, 2002
    Date of Patent: July 29, 2003
    Assignee: Motorola, Inc.
    Inventors: Joseph J. Nahas, Thomas W. Andre, Bradley J. Garni, Chitra K. Subramanian
  • Patent number: 6580298
    Abstract: A sense amplifier having three inputs determines the state of a memory bit cell by converting a bit input voltage, a high reference voltage, and a low reference voltage to respective current values. Current differences are formed between a bit current and a high reference current, and between a low reference current and a bit current. Current mirrors (154, 158 and 170, 166) and loads (160 and 168) are used in conjunction with current steering circuitry (150, 140, 142 and 162) to form the difference of the bit current and the high reference current and also form the difference of the low reference current and the bit current. Additionally, the sense amplifier drives differential outputs (OUT and OUT13B) to reflect the difference between the two current differential quantities.
    Type: Grant
    Filed: June 28, 2002
    Date of Patent: June 17, 2003
    Assignee: Motorola, Inc.
    Inventors: Chitra K. Subramanian, Bradley J. Garni, Joseph J. Nahas, Thomas W. Andre
  • Publication number: 20030055717
    Abstract: A system and method is provided for automatically promoting a representative in a network marketing organization which includes multiple career levels. The representative is associated with account information. The system accepts application information and updates the account information. The system retrieves a plurality of promotion parameters and the updated account information and applies the promotion parameters to the account information to determine if the representative qualifies for a promotion. If the representative qualifies for a promotion, the system automatically updates the representative's career level with a new career level.
    Type: Application
    Filed: May 18, 2001
    Publication date: March 20, 2003
    Inventors: Ujwal Rao Badugu, Srikantappa Ravi Kumar, Shriram K. Subramanian, Jerry Gene Wood
  • Patent number: 6413819
    Abstract: A semiconductor device that includes a floating gate made up of a plurality of pre-formed isolated storage elements (18) and a method for making such a device is presented. The device is formed by first providing a semiconductor layer (12) upon which a first gate insulator (14) is formed. A plurality of pre-fabricated isolated storage elements (18) is then deposited on the first gate insulator (14). This deposition step may be accomplished by immersion in a colloidal solution (16) that includes a solvent and pre-fabricated isolated storage elements (18). Once deposited, the solvent of the solution (16) can be removed, leaving the pre-fabricated isolated storage elements (18) deposited on the first gate insulator (14). After depositing the pre-fabricated isolated storage elements (18), a second gate insulator (20) is formed over the pre-fabricated isolated storage elements (18).
    Type: Grant
    Filed: June 16, 2000
    Date of Patent: July 2, 2002
    Assignee: Motorola, Inc.
    Inventors: Sufi Zafar, Ramachandran Muralidhar, Bich-Yen Nguyen, Sucharita Madhukar, Daniel T. Pham, Michael A. Sadd, Chitra K. Subramanian
  • Patent number: 6297095
    Abstract: A semiconductor memory device with a floating gate that includes a plurality of nanoclusters (21) and techniques useful in the manufacturing of such a device are presented. The device is formed by first providing a semiconductor substrate (12) upon which a tunnel dielectric layer (14) is formed. A plurality of nanoclusters (19) is then grown on the tunnel dielectric layer (14). After growth of the nanoclusters (21), a control dielectric layer (20) is formed over the nanoclusters (21). In order to prevent oxidation of the formed nanoclusters (21), the nanoclusters (21) may be encapsulated using various techniques prior to formation of the control dielectric layer (20). A gate electrode (24) is then formed over the control dielectric (20), and portions of the control dielectric, the plurality of nanoclusters, and the gate dielectric that do not underlie the gate electrode are selectively removed.
    Type: Grant
    Filed: June 16, 2000
    Date of Patent: October 2, 2001
    Assignee: Motorola, Inc.
    Inventors: Ramachandran Muralidhar, Chitra K. Subramanian, Sucharita Madhukar, Bruce E. White, Michael A. Sadd, Sufi Zafar, David L. O'Meara, Bich-Yen Nguyen
  • Patent number: 5958508
    Abstract: A metal-semiconductor layer (26) is formed over an insulating layer (20) such that the metal-semiconductor layer (26) is graded to have varying amounts of the semiconductor and metal throughout the layer. In one embodiment, the metal-semiconductor layer (26) has relatively higher silicon content near the layer's lower and upper surfaces. At the midpoint, the layer is close to stoichiometric tungsten silicide. In another embodiment, a metal-semiconductor-nitrogen layer is formed having nitrogen nearer the lower surface and essentially no nitrogen near the upper surface. The layer (26) can be formed using chemical vapor deposition or sputtering.
    Type: Grant
    Filed: March 31, 1997
    Date of Patent: September 28, 1999
    Assignee: Motorlola, Inc.
    Inventors: Olubunmi Olufemi Adetutu, Dean J. Denning, James D. Hayden, Chitra K. Subramanian, Arkalgud R. Sitaram
  • Patent number: 5824579
    Abstract: A shared contact structure (30) is formed to electrically connect three coupling layers (59,60,46) to each other and to an active region (33) in a semiconductor substrate (31). A first coupling layer (59) and a second coupling layer (60) are formed such that they are physically isolated from each other. The second coupling layer (60) is formed such that it is in physical contact with the active region (33). A contact opening (45) is formed, which exposes a portion of coupling layers (59, 60). The third coupling layer (46) is then formed so that it is in electrical contact with the second coupling layer (60) and the first coupling layer (59).
    Type: Grant
    Filed: April 15, 1996
    Date of Patent: October 20, 1998
    Assignee: Motorola, Inc.
    Inventors: Chitra K. Subramanian, James D. Hayden
  • Patent number: 5668021
    Abstract: A process for fabricating an MOS device (44) having a segmented channel region (48) includes the fabrication of a compound MOS gate electrode (46). Both the segmented channel region (48) and the MOS gate electrode (46) are formed by creating an opening (18) and an insulating layer (16) overlying a first polycrystalline silicon layer (14). The lateral extent of both the MOS gate electrode (46) and a buried junction region (24) formed in the semiconductor substrate (10) are defined by first sidewall spacer (22) and a second sidewall spacer (32) formed adjacent to the first sidewall spacer (22).
    Type: Grant
    Filed: June 4, 1996
    Date of Patent: September 16, 1997
    Assignee: Motorola, Inc.
    Inventors: Chitra K. Subramanian, James D. Hayden
  • Patent number: 5665202
    Abstract: A process for polish planarizing a fill material (40) overlying a semiconductor substrate (30) includes a multi-step polishing process. In one embodiment, a second planarization layer (42) is deposited over a fill material (40) and a portion of the fill material (40) is removed leaving a remaining portion (44). The pad pressure of a CMP apparatus (20) is adjusted such that a first pressure is generated during the polishing process. Then, the remaining portion (44) is removed, while operating the CMP apparatus (20) at a second pad pressure. The selectivity of the polishing process is maintained by reducing the pad pressure during the second polishing step. In a second embodiment, after the first polishing step is performed, the remaining portion (44) is removed by an etching process using a portion (46) of second planarization layer (42).
    Type: Grant
    Filed: November 24, 1995
    Date of Patent: September 9, 1997
    Assignee: Motorola, Inc.
    Inventors: Chitra K. Subramanian, Asanga H. Perera, James D. Hayden, Subramoney V. Iyer
  • Patent number: 5494837
    Abstract: A method of forming a semiconductor-on-insulator (SOI) electronic device includes the steps of etching a semiconductor substrate to form a plurality of adjacent trenches therein and then forming electrically insulating layers on bottoms of the trenches. Epitaxial lateral overgrowth (ELO) is then performed to grow respective monocrystalline semiconducting regions in the trenches. These semiconducting regions are preferably grown from a sidewall of each trench onto a respective insulating layer and fill each trench. Monocrystalline active regions of the electronic device are then formed in the semiconducting regions and also in the substrate, adjacent the trench sidewalls. For example, a monocrystalline trench isolated extrinsic base region of a bipolar junction transistor (BJT) can be formed in a semiconducting region in a respective trench, and a corresponding intrinsic base region and an intrinsic collector region can be formed in the substrate, adjacent the semiconducting region.
    Type: Grant
    Filed: September 27, 1994
    Date of Patent: February 27, 1996
    Assignee: Purdue Research Foundation
    Inventors: Chitra K. Subramanian, Gerold W. Neudeck