Patents Assigned to National Semiconductor Corp.
  • Patent number: 5731812
    Abstract: A display protection circuit includes a first OR gate which receives a first pulse at one input and a first clock signal at another input. A second OR gate receives the first pulse at one input and a second clock signal at another input. A first monostable multivibrator is coupled to the first OR gate and receives an output of the first OR gate and generates a second pulse in response thereto. A second monostable multivibrator is coupled to the second OR gate and receives an output of the second OR gate and generates a third pulse in response thereto. A first logic gate is coupled to the first and second monostable multivibrators and generate a fourth pulse which changes state in response to one of the first and second clock signals stopping transitioning for a first predetermined period of time.
    Type: Grant
    Filed: May 26, 1995
    Date of Patent: March 24, 1998
    Assignee: National Semiconductor Corp.
    Inventor: Daniel R. Herrington
  • Patent number: 5705419
    Abstract: In the manufacture of memory cells, horizontal etching is controlled in a manner which prevents the formation of stringers between adjacent cells without undercutting the sidewalls of a memory cell.
    Type: Grant
    Filed: July 27, 1994
    Date of Patent: January 6, 1998
    Assignee: National Semiconductor Corp.
    Inventors: Jeffrey Robert Perry, S. M. Reza Sadjadi, Kristen Ann Luttinger
  • Patent number: 5706059
    Abstract: A hierarchial search for moving image encoding determines a motion vector by comparing a target block to sets of blocks selected according to the results of previous comparisons. Typically, each set of blocks includes a central block and four blocks offset on x and y axes. Blocks most similar to the target block provide co-ordinates of a center block in a next stage of the search. The hierarchial search searches regions indicated by previous comparisons to be similar to the target block and thereby reduces the number of comparisons and the search time required to find a motion vector. A motion estimation circuit for the hierarchial search includes: five processing elements which compare the target block to five blocks; a first memory that asserts a target block pixel value to the processing elements; a second memory that asserts five search window pixel values to the processing elements.
    Type: Grant
    Filed: November 30, 1994
    Date of Patent: January 6, 1998
    Assignee: National Semiconductor Corp.
    Inventors: Xiaonong Ran, Michael van Scherrenburg
  • Patent number: 5687102
    Abstract: A double precision shift operation utilizes a 32 bit data path.
    Type: Grant
    Filed: May 26, 1995
    Date of Patent: November 11, 1997
    Assignee: National Semiconductor Corp.
    Inventor: Thomas William Schaw Thomson
  • Patent number: 5679405
    Abstract: A suitable inert thermal gas such as argon is introduced onto the backside of wafers being processed in a CVD reactor during the deposition of tungsten or other metals and silicides, to avoid deposition of material on the backside of the wafers being processed. Each process station includes a gas dispersion head disposed over a platen. The platen has a circular depression for receiving a wafer, and an annular groove provided in the floor of the depression, near the wall thereof. Heated and pressurized backside gas is introduced into the groove so that the wafer is maintained in a position above the floor of the depression but still within it. In this manner, backside gas vents from beneath the edge of the wafer on the platen and prevents the process gases from contacting the wafer backside. The backside gas is also used for levitating the wafer in a transfer region above the platen, so that the wafer can be transported to or from the platen with a suitable wafer transfer mechanism.
    Type: Grant
    Filed: July 24, 1995
    Date of Patent: October 21, 1997
    Assignees: National Semiconductor Corp., Novellus Systems, Inc.
    Inventors: Michael E. Thomas, Everhardus P. van de Van, Eliot K. Broadbent
  • Patent number: 5654702
    Abstract: A variable length coding process encodes a string of symbol values using arithmetic coding models selected according to the syntax of the string. The arithmetic coding models are optimized for each separate symbol in the string to provide efficient coding that provides a shorter average code length than is provided with arithmetic coding using a single model. In an embodiment for moving image coding, two sets of arithmetic coding models, one for intra frames and one for inter frames, are used for a series symbols representing DCT blocks. The model used for a symbol depends of the symbol's value and order in the series.
    Type: Grant
    Filed: December 16, 1994
    Date of Patent: August 5, 1997
    Assignee: National Semiconductor Corp.
    Inventor: Xiaonong Ran
  • Patent number: 5614444
    Abstract: A method of using additives with silica-based slurries to enhance metal selectivity in polishing metallic materials utilizing a chemical-mechanical polishing (CMP) process. Additives are used with silica-based slurries to passivate a dielectric surface, such as a silicon dioxide (SiO.sub.2) surface, of a semiconductor wafer so that dielectric removal rate is reduced when CMP is applied. The additive is comprised of at least a polar component and an apolar component. The additive interacts with the surface silanol group of the SiO.sub.2 surface to inhibit particles of the silica-based slurry from interacting with hydroxyl molecules of the surface silanol group. By applying a surface passivation layer on the SiO.sub.2 surface, erosion of the SiO.sub.2 surface is reduced. However, the metallic surface is not influenced significantly by the additive, so that the selectivity of metal removal over oxide removal is enhanced.
    Type: Grant
    Filed: June 6, 1995
    Date of Patent: March 25, 1997
    Assignees: Sematech, Inc., Intel Corporation, National Semiconductor Corp., Digital Equipment Corp.
    Inventors: Janos Farkas, Rahul Jairath, Matt Stell, Sing-Mo Tzeng
  • Patent number: 5592113
    Abstract: An error-limiting circuit for regulating the time required to bring the output signal of a control system such as a phase-locked loop device into conformance with a reference input signal. For a phase-locked loop system the error-limiting circuit is a phase-error-limiting circuit that provides for a gradual changing of the signal frequency of a voltage-controlled oscillator of the phase-locked loop device so that frequency synchronization of subsequent devices coupled to the phase-locked loop with the reference signal is ensured. The phase-error-limiting circuit forms part of the phase-frequency detector that is coupled to a charge pump that outputs current to a loop filter that in turn effectively controls the voltage-controlled oscillator. The phase-error-limiting circuit acts to assert or de-assert as required an error-correcting UP or DOWN signal to the charge pump.
    Type: Grant
    Filed: March 28, 1995
    Date of Patent: January 7, 1997
    Assignee: National Semiconductor Corp.
    Inventors: Duane G. Quiet, E. Wayne Porter
  • Patent number: 5566203
    Abstract: A physical layer (PHY) device which can operate as a conventional PHY or as an intelligent repeater in a communication system. The PHY device supports four optional modes which may be enabled by programming control register bits with a microcontroller. These optional modes are: pass all symbols, enable noise filter, pass violation symbols and pass line states. During operation as an intelligent repeater, the pass all symbols, pass violation symbols and pass line states modes are enabled. The intelligent repeater allows errors in a data stream to be encoded and repeated without filtering to a downstream station. The intelligent repeater also allows line states to be repeated without station management software. A single intelligent repeater may be used to couple two stations or multiple intelligent repeaters may be connected to form multi-port repeater boxes which can be connected to facilitate more reliable connections between stations.
    Type: Grant
    Filed: June 24, 1993
    Date of Patent: October 15, 1996
    Assignee: National Semiconductor Corp.
    Inventors: David C. Brief, Gregory L. DeJager, James R. Hamstra
  • Patent number: 5557567
    Abstract: Multiple logic levels can be simultaneously programmed into any combination of memory cells in a column of an alternate-metal virtual-ground (AMG) EPROM or flash memory array by applying one of a corresponding number of programming voltages to the word lines that correspond with the cells to be programmed. In the present invention, the memory cells in the array form a punchthrough current during programming which, in turn, leads to the formation of an increased number of substrate hot electrons. By utilizing the substrate hot electrons formed from the punchthrough current in addition to the channel hot electrons, much lower control gate voltages can be utilized during programming.
    Type: Grant
    Filed: April 6, 1995
    Date of Patent: September 17, 1996
    Assignee: National Semiconductor Corp.
    Inventors: Albert Bergemont, Min-hwa Chi
  • Patent number: 5546045
    Abstract: An integrated circuit output stage is intended for use with an operational amplifier. The output is capable of driving capacitive load to within a V.sub.SAT of the power supply rails. The complementary output transistors are driven by way of a combination of buffers and complementary differential amplifiers which act to bias the stage in class AB. The quiescent current is stabilized and controlled, in part, by simple resistor rationing. The output transistor saturation is sensed and a current limit is imposed so that hard saturation is avoided. Frequency compensation is achieved in a manner that responds to output transistor saturation so as to improve the high frequency transient response. Feedforward capacitors are also included to further improve high frequency response.
    Type: Grant
    Filed: April 19, 1995
    Date of Patent: August 13, 1996
    Assignee: National Semiconductor Corp.
    Inventor: Don R. Sauer
  • Patent number: 5543746
    Abstract: A temperature compensation circuit is disclosed that includes a first field-effect transistor (FET), a second FET, a resistor, and current generating circuitry. The second FET has a larger current conducting channel than the current conducting channel of the first FET, and the gate of the second FET is coupled to the gate of the first FET. The resistor is coupled between a first node that is common with the source of the first FET and a second node that is common with the source of the second FET. The current generating circuitry generates and maintains substantially equal drain currents in the first and second FETs.
    Type: Grant
    Filed: August 22, 1995
    Date of Patent: August 6, 1996
    Assignee: National Semiconductor Corp.
    Inventor: James R. Kuo
  • Patent number: 5537064
    Abstract: A protection circuit for a semiconductor switch for switching a load is disclosed. Control circuitry is used for switching the semiconductor switch on in response to a switching signal and for switching the semiconductor switch off in response to a deactivation signal. A deactivation circuit is used for generating the deactivation signal. An overvoltage detector circuit responsive to a voltage at an output of the semiconductor switch that exceeds a predetermined value is used for generating an overvoltage signal. The overvoltage detector circuit includes a Zener diode that has its cathode coupled through a resistor to the output of the semiconductor switch and its anode coupled to the collector of the diode connected transistor. A first logic circuit is used for causing the deactivation circuit to generate the deactivation signal in response to the switching signal and the overvoltage signal.
    Type: Grant
    Filed: April 27, 1995
    Date of Patent: July 16, 1996
    Assignee: National Semiconductor Corp.
    Inventors: Robert A. Pease, Robin Shields
  • Patent number: 5535086
    Abstract: An ESD protection circuit for a BICMOS IC device protects NMOS transistors (Q2) of internal CMOS gates (G2) from ESD events at a high potential power rail (VCC). Specifically the ESD protection circuit protects NMOS pulldown transistors coupled between a pullup bipolar emitter follower transistor (Q5) and the low potential power rail (GND). A PMOS current control transistor (QPESD) is coupled with primary current path between the high potential power rail (VCC) and the bipolar emitter follower transistor (Q5) for controlling current flow through the emitter follower transistor. An RC time constant circuit (R10,C1) is coupled between the high potential power rail (VCC) and low potential power rail (GND). The RC time constant circuit is constructed with a time constant for following power up events but not for following the faster ESD events at the high potential power rail.
    Type: Grant
    Filed: September 22, 1994
    Date of Patent: July 9, 1996
    Assignee: National Semiconductor Corp.
    Inventor: Ray A. Mentzer
  • Patent number: 5535219
    Abstract: A pointer processing circuit processes SONET/SDH frames and calculates a new pointer value. A pointer interpreter circuit (PI) is constructed to receive an incoming frame, identify the pointer in transport overhead bytes of the frame, interpret the pointer, and send the pointer value directly to a pointer generator circuit (PG). The pointer value indicates the position of the first byte of the data payload bytes of the incoming frame starting at the trace byte J1. The PI is constructed to tag the next data byte after the pointer H1 H2 and negative justification data holding byte location H3 and send the tagged data byte directly to a FIFO without the delay of counting down to the trace byte J1 of the incoming frame. A first in first out memory FIFO is coupled to the PI for writing data payload bytes from the incoming frame into the FIFO. A pointer generator circuit (PG) is coupled to the FIFO for changing the pointer on the outgoing frame.
    Type: Grant
    Filed: June 14, 1995
    Date of Patent: July 9, 1996
    Assignee: National Semiconductor Corp.
    Inventor: Oscar W. Freitas
  • Patent number: 5508702
    Abstract: A digital-to-analog conversion device that has one or more conversion cells, each cell coupled to a master voltage source and to a specific binary input element. The conversion cells include binary-weighted or binary-sized output transistors such that each output transistor, when called upon, delivers a unique analog output current corresponding to a particular binary signal. The master potential provided by a stable source is supplied to the control nodes of the output transistors so that the potential at those control nodes remains constant. Switching on and off of the output transistors is achieved by regulating the sources of those transistors rather than their gates. By regulating the operation of the output transistors at their sources, the present invention provides a digital-to-analog converter and a conversion method with little switching noise and minimal switching delay.
    Type: Grant
    Filed: June 17, 1994
    Date of Patent: April 16, 1996
    Assignee: National Semiconductor Corp.
    Inventors: Julio R. Estrada, Ray A. Mentzer
  • Patent number: 5488289
    Abstract: A voltage to current converter which exhibits a well-defined substantially exponential voltage-current characteristic. First and second input bipolar transistors of the voltage to current converter each have an emitter, a base, and a collector. The first and second input bipolar transistors are coupled at their emitters, and may be biased with a pre-determined constant current source, and they accept a selectable differential input voltage at their bases. A reference current source is connected to the collector of the first input bipolar transistor, and all output current source is connected to the collector of the second input bipolar transistor. A feedback element, having a gain, is connected between the coupled emitters and the collector of the first input bipolar transistor. The feedback element senses a voltage at the collector of the first input bipolar transistor and regulates a voltage at the coupled emitters to maintain a constant current through said first input bipolar transistor.
    Type: Grant
    Filed: November 18, 1993
    Date of Patent: January 30, 1996
    Assignee: National Semiconductor Corp.
    Inventor: Pak-Ho Yeung
  • Patent number: 5478435
    Abstract: A point of use slurry dispensing system with controls for dilution, temperature and oxidizer/etchant/additive infusion. A slurry in unmixed form and a diluting agent are independently pumped to a pad on a CMP tool. Liquid heaters are used to heat the slurry and the diluting agent to a desirable temperature. The actual mixing occurs at the point of use on the pad or in a dispensing line just prior to the point of use. In some instances a third independent distribution line is used to dispense an oxidizer, etchant and/or chemical additive at or near the point of use.
    Type: Grant
    Filed: December 16, 1994
    Date of Patent: December 26, 1995
    Assignees: National Semiconductor Corp., Sematech Inc., AT&T GIS
    Inventors: James J. Murphy, Janos Farkas, Lucia C. Markert, Rahul Jairath
  • Patent number: 5468990
    Abstract: Embodiments according to the present invention provide tamper resistant structures which make it more difficult to reverse engineer integrated circuits. In one embodiment, a tamper resistant structure on a passivation layer leaves portions of the passivation layer exposed. Mechanical or chemical removal of the tamper resistant structure damages exposed portions of the passivation layer and makes reverse engineering difficult. Other embodiments of the tamper resistant structure include patterned and unpatterned structures containing hard materials, chemically resistant materials, amalgams, fibrous materials, and/or meshes attached to a passivation layer. Tamper resistant structures can also be provided between layers of the active circuitry.
    Type: Grant
    Filed: July 22, 1993
    Date of Patent: November 21, 1995
    Assignee: National Semiconductor Corp.
    Inventor: Keith E. Daum
  • Patent number: 5455793
    Abstract: A novel nonvolatile memory cell structure is provided using a non-self aligned CMOS process with two independent N+ implants using a two or a three polysilicon layer technology that allows in-circuit electrical erase and reprogramming together with reduction in cell size requirement. The novel memory cell is implemented with a merged transistor structure having an access transistor and a programmable transistor. The memory cell is constructed by having the control gate, formed of a first polysilicon layer, covering a portion of the channel length between drain and source to form the access portion of the merged transistors, and a floating gate formed of a second polysilicon layer overlapping a second portion of the channel length to form the programmable transistor portion of the merged transistor. Such merged transistor structure is equivalent to two transistors in series, a programmable transistor in series with an access transistor.
    Type: Grant
    Filed: November 17, 1994
    Date of Patent: October 3, 1995
    Assignee: National Semiconductor Corp.
    Inventors: Alaaeldin A. M. Amin, James Brennan, Jr.