Patents by Inventor Fernando D. Carvajal
Fernando D. Carvajal 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: 7202710Abstract: An apparatus for handling signaling between a sending device and a receiving device includes: (a) a buffering amplifier device having at least one input locus for receiving an input signal from the receiving device and having at least one output locus for presenting an output signal for the receiving device; each respective at least one output locus presents an output signal in response to the input signal received at a respective input locus of the at least one input locus; (b) a feed forward circuit coupling each respective input locus with its respective corresponding output locus to provide a feed forward signal to the respective corresponding output locus; the feed forward signal is in phase with the input signal received at the respective input locus.Type: GrantFiled: April 30, 2004Date of Patent: April 10, 2007Assignee: Texas Instruments IncorporatedInventors: Fernando D. Carvajal, Yanli Fan
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Patent number: 6744280Abstract: System and methods are provided for monitoring circuit performance and correcting for variations in current reference signals to maintain a desired Voltage Output Differential (VOD) between the two differential output signals. A voltage signal associated with VOD is compared to a signal that is set to a desired voltage level based on a desired VOD. By determining whether the VOD level is higher or lower than the desired level, adjustments are made to at least one of an output current source level and an output current sink level. An increase in the source and sink currents at the output results in an increased VOD, while a balance decrease in the source and sink currents results in a decreased VOD.Type: GrantFiled: May 9, 2002Date of Patent: June 1, 2004Assignee: Texas Instruments IncorporatedInventors: Mark W. Morgan, Fernando D. Carvajal
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Publication number: 20030184349Abstract: Transitions (e.g. high to low and/or low to high) associated with operation of the driver are employed to implement control, which can be applied as a pulse in response to an occurrence of the transition. The control operates to speed up the transition at the output of the driver, such as can reduce driver switching times and enable a corresponding increase in data transmission rates.Type: ApplicationFiled: April 2, 2002Publication date: October 2, 2003Inventors: Fernando D. Carvajal, Mark W. Morgan, Srikanth Gondi
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Patent number: 6628150Abstract: Transitions (e.g. high to low and/or low to high) associated with operation of the driver are employed to implement control, which can be applied as a pulse in response to an occurrence of the transition. The control operates to speed up the transition at the output of the driver, such as can reduce driver switching times and enable a corresponding increase in data transmission rates.Type: GrantFiled: April 2, 2002Date of Patent: September 30, 2003Assignee: Texas Instruments IncorporatedInventors: Fernando D. Carvajal, Mark W. Morgan, Srikanth Gondi
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Patent number: 6617846Abstract: A method for isolatively coupling an input signal to an output signal, where the input signal is a first voltage differential, comprises three steps. Step one calls for generating a magnetic field that is indicative of the input signal in at least one magnetic sensor in an integrated circuit by generating a current through a conductor in the integrated circuit. The current is generated by applying the first voltage differential across the conductor, which is proximate the magnetic sensor. Step two requires generating a second voltage differential between two points of the magnetic sensor by providing a current through the magnetic sensor in a direction having a component transverse to the magnetic field. Step three calls for providing a signal indicative of the second voltage differential as the output signal, thereby isolatively coupling the input signal to the output signal.Type: GrantFiled: August 27, 2001Date of Patent: September 9, 2003Assignee: Texas Instruments IncorporatedInventors: Kambiz Hayat-Dawoodi, Fernando D. Carvajal
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Patent number: 6538500Abstract: A differential line driver with 4X supply voltage swing with a 1:1 transformer, which enhances the loop length for applications such as digital subscriber line includes: a differential circuit having first and second input nodes, first and second output nodes 52 and 54, and a supply voltage node; a transformer 22 having a first coil coupled between the first and second output nodes; and a center tap 50 of the first coil coupled to the supply voltage node. The device also acts as an active impedance termination, which eliminates the series termination resistor in conventional hybrids and thereby saving 6 dB transmit power.Type: GrantFiled: August 24, 2001Date of Patent: March 25, 2003Assignee: Texas Instruments IncorporatedInventors: Kambiz Hayat-Dawoodi, Anil Kumar, Fernando D. Carvajal
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Patent number: 6480029Abstract: A low voltage 485-driver circuit that meets the standard leakage and 1.5 voltage differential output requirements of the TIA/EIA-485 specification while operating from a 3V supply. The circuit avoids the voltage drop across the series Schottky diodes in the output driver of a conventional 485-driver by moving the Schottky blocking diodes from the output stage signal path to the pre-driver stage so that the output stage is restricted to back-gate biasing only. In addition, the circuit uses stacked NMOS transistors to maintain lower voltage across each NMOS transistor in order to prevent hot-carrier injection. This allows lower voltage rated output NMOS transistors to be used, resulting in higher speed operation. The circuit will withstand excessive common mode voltages in the range of +12V to −7V applied to the output while in either signaling ON state or the disabled OFF state.Type: GrantFiled: June 26, 2001Date of Patent: November 12, 2002Assignee: Texas Instruments IncorporatedInventors: Mark W. Morgan, Fernando D. Carvajal, Roy C. Jones, III
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Patent number: 6369621Abstract: A fast voltage differential signaling (LVDS) transceiver (50) having high repeater speeds up to 1.36 GBps, and also meeting the TIA/EIA-644 standard short-to-ground requirements. A mixed voltage-current mode differential driver has a respective control signal (A3) driving each of the drive transistors (Q3). The control signal (A3) is controlled by a transistor (M1) being a function of current through the respective drive transistor (Q3). A current mirror (Q4, Q5, Q6) is used to mirror current conducting through a transistor (Q4) in parallel with the drive transistor (Q3), which mirror current is compared against a current reference (Iref).Type: GrantFiled: March 29, 2001Date of Patent: April 9, 2002Assignee: Texas Instruments IncorporatedInventors: Steven J. Tinsley, Fernando D. Carvajal
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Publication number: 20020027488Abstract: A method for isolatively coupling an input signal to an output signal, where the input signal is a first voltage differential, comprises three steps. Step one calls for generating a magnetic field that is indicative of the input signal in at least one magnetic sensor in an integrated circuit by generating a current through a conductor in the integrated circuit. The current is generated by applying the first voltage differential across the conductor, which is proximate the magnetic sensor. Step two requires generating a second voltage differential between two points of the magnetic sensor by providing a current through the magnetic sensor in a direction having a component transverse to the magnetic field. Step three calls for providing a signal indicative of the second voltage differential as the output signal, thereby isolatively coupling the input signal to the output signal.Type: ApplicationFiled: August 27, 2001Publication date: March 7, 2002Inventors: Kambiz Hayat-Dawoodi, Fernando D. Carvajal
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Publication number: 20020024381Abstract: A differential line driver with 4×supply voltage swing with a 1:1 transformer, which enhances the loop length for applications such as digital subscriber line includes: a differential circuit having first and second input nodes, first and second output nodes 52 and 54, and a supply voltage node; a transformer 22 having a first coil coupled between the first and second output nodes; and a center tap 50 of the first coil coupled to the supply voltage node. The device also acts as an active impedance termination, which eliminates the series termination resistor in conventional hybrids and thereby saving 6 dB transmit power.Type: ApplicationFiled: August 24, 2001Publication date: February 28, 2002Inventors: Kambiz Hayat-Dawoodi, Anil Kumar, Fernando D. Carvajal
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Publication number: 20020021144Abstract: A low voltage 485-driver circuit that meets the standard leakage and 1.5 voltage differential output requirements of the TIA/EIA-485 specification while operating from a 3V supply. The circuit avoids the voltage drop across the series Schottky diodes in the output driver of a conventional 485-driver by moving the Schottky blocking diodes from the output stage signal path to the pre-driver stage so that the output stage is restricted to back-gate biasing only. In addition, the circuit uses stacked NMOS transistors to maintain lower voltage across each NMOS transistor in order to prevent hot-carrier injection. This allows lower voltage rated output NMOS transistors to be used, resulting in higher speed operation. The circuit will withstand excessive common mode voltages in the range of +12V to −7V applied to the output while in either signaling ON state or the disabled OFF state.Type: ApplicationFiled: June 26, 2001Publication date: February 21, 2002Inventors: Mark W. Morgan, Fernando D. Carvajal, Roy C. Jones, III
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Patent number: 6320406Abstract: An active fail-safe method and apparatus for a LVDS receiver that uses a window comparator circuit to monitor the differential voltage at the receiver's input pins and drive the output to a known logic HIGH state in the absence of a valid input signal; i.e., when the input differential signal is less than a chosen threshold value of approximately 80 mV. Such a condition may occur when the cable is removed or damaged in such a way that no valid input signal is present. In the presence of a valid input signal, the circuit's output tracks the differential input without any degradation to the signal.Type: GrantFiled: October 2, 2000Date of Patent: November 20, 2001Assignee: Texas Instruments IncorporatedInventors: Mark W. Morgan, Fernando D. Carvajal, Kevin J. Gingerich
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Patent number: 6278336Abstract: A low-current oscillator with input buffer hysteresis for increased noise immunity during oscillator start-up. Resistors are switched in and out of the comparator input elements creating offsets in one leg of the comparator at a time.Type: GrantFiled: February 25, 1999Date of Patent: August 21, 2001Assignee: Texas Instruments IncorporatedInventors: Steven J. Tinsley, Fernando D. Carvajal
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Patent number: 6246262Abstract: A three-state CMOS output buffer (200), having protective circuitry and an output node (OUT) connected to a bus, prevents damage to a connected integrated circuit when the bus voltage exceeds a power supply reference voltage (VCC). A final output stage of the output buffer (200) includes a first pull-up transistor (QP200), a clamping transistor (QN202), and a pull-down transistor (QN204). A half-pass circuit (QN200) blocks the output voltage from propagating through the final output stage to damage the output buffer (200) when the output voltage applied to the output node (OUT) exceeds the supply voltage. The protective circuitry uses a clamping circuit (210), a switching circuit (212) and a backgate bias circuit (206) to prevent a leakage path between the output node (OUT) and the power supply reference (VCC) through the source/bulk junction of biased transistors in the output buffer (200).Type: GrantFiled: February 24, 2000Date of Patent: June 12, 2001Assignee: Texas Instruments IncorporatedInventors: Mark W. Morgan, Fernando D. Carvajal
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Patent number: 6236254Abstract: A circuit (10) operates at relatively low values of the supply voltage, and includes a differential input circuit (16) which receives a differential input signal at first and second terminals (18, 21). A differential voltage derived by the input circuit from the differential input signal is present at third and fourth terminals (28, 31) and is amplified by a differential amplifier (12). A differential level adjuster (14) adjusts output voltages from the amplifier to suitable values for application to a matcher (15). The matcher (15) generates two currents that also flow within a differential compensator (17), and that match respective currents flowing in the amplifier. The differential compensator then provides a suitable current to each of the third and fourth terminals, such that the current flow between the first and third terminals, and between the second and fourth terminals, is substantially zero.Type: GrantFiled: July 17, 2000Date of Patent: May 22, 2001Assignee: Texas Instruments IncorporatedInventors: Mark W. Morgan, Fernando D. Carvajal
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Patent number: 6087852Abstract: The invention is a multiplex circuit for outputing two or more signals of different levels to a common output pad where a first output driver (D.sub.h) is powered from a voltage rail having a higher voltage than at least one second output driver (D.sub.1) power by a lower voltage rail. An interface circuit (IFC) and level shift circuit provides two output signals base on a single input signal, one signal being equivalent to the voltage of the higher voltage (V.sub.High) and the other being based on the lower voltage (V.sub.low). PMOS device connected to the output pad has its back gate connected to V.sub.high to prevent leakage current through the PMOS device when the output to the output pad (P.sub.1) is equivalent to V.sub.High.Type: GrantFiled: December 8, 1998Date of Patent: July 11, 2000Assignee: Texas Instruments IncorporatedInventors: David D. Briggs, Fernando D. Carvajal, Chao-Chih Chiu
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Patent number: 5710499Abstract: A stepper control circuit and method for providing improved stepper motor control is provided. In a first embodiment, output drivers having three states are used to drive the coil terminals of an exemplary stepper motor. The use of the three state output drivers provides rapid discharge of the current stored in the coils of the motor, allowing faster operation of the stepper motor, and prevents erroneous skipping of steps, as occurred with prior art circuitry. A detailed implementation of the preferred embodiment is described. An integrated circuit including the stepper motor control circuitry of the first preferred embodiment is described.Other devices, systems and methods are also disclosed.Type: GrantFiled: September 30, 1994Date of Patent: January 20, 1998Assignee: Texas Instruments IncorporatedInventor: Fernando D. Carvajal
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Patent number: 5633651Abstract: A bidirectional indicator driver circuit having automatic current sensing for driving an indicator regardless of its orientation. A comparator is coupled to memory which has an output indicating a driving direction polarity. An output driver which drives one terminal of a plurality of LED diodes is coupled to the memory. Individual three state buffers are coupled to the second terminal of each of the respective LEDs. The comparator detects whether the output driver is driving current. If no current is being driven to the LEDs, the comparator causes the memory to toggle states, and toggles the level of the polarity signal. Because the polarity signal is coupled to one terminal of the LEDs, the change in polarity will automatically cause one or more of the LEDs to be forward biased and emit light.Type: GrantFiled: November 4, 1994Date of Patent: May 27, 1997Assignee: Texas Instruments IncorporatedInventors: Fernando D. Carvajal, Stephen C. Kwan
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Patent number: 5629609Abstract: A low voltage drop out circuit (10) has a voltage regulating transistor (13) between a supply voltage (12) and an output terminal (28). An active feedback loop controls the voltage regulating transistor (13) according to a magnitude of the supply voltage (12) to control the voltage on the output terminal (28). A reference voltage source (25) produces a reference voltage, and a switch, which may be a second transistor (45) of similar type than the voltage regulating transistor (13), is connected in parallel with the voltage regulating transistor (13). A comparing circuit (42) detects when the supply voltage (12) falls below the reference voltage (25) to operate the second transistor (45), which may be sized to be much larger than the voltage regulating transistor (13) to effectively short across the voltage regulating transistor (13) when the supply voltage (12) falls below a predetermined level.Type: GrantFiled: March 8, 1994Date of Patent: May 13, 1997Assignee: Texas Instruments IncorporatedInventors: Baoson Nguyen, Fernando D. Carvajal
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Patent number: 5625278Abstract: The voltage regulator circuit contains a MOS transistor 12 connected between a voltage supply line 22 and an output line 30. The MOS transistor 12 provides a stable voltage on the output line 30 independent of voltage transients on the voltage supply line 22 and independent of current transients on the output line 30. An amplifier 14 coupled to the MOS transistor 12 controls the response of the MOS transistor 12. Feedback circuitry connected between the output line 30 and the amplifier 14 provides feedback to the amplifier 14. A voltage source 16 provides the reference for amplifier 14.Type: GrantFiled: March 28, 1996Date of Patent: April 29, 1997Assignee: Texas Instruments IncorporatedInventors: Frank L. Thiel, Todd M. Neale, Baoson Nguyen, Fernando D. Carvajal