Patents by Inventor William A. Burkland
William A. Burkland 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: 7679420Abstract: A level shifter circuit includes two parallel current paths respectively controlled by switch transistors, a Wilson current mirror circuit, and a slew rate control circuit to selectively couple an output node either to a high (first) voltage source or to a ground (second voltage) source in response to differential input control signals signal. When the output node reaches a stable (high or low) voltage level, the low voltage on one of the current paths turns off a Wilson current mirror transistor in the other current path, thereby preventing quiescent current during stable periods. An optional cascode transistor is added to facilitate fabrication using low threshold voltage transistors.Type: GrantFiled: August 28, 2008Date of Patent: March 16, 2010Assignee: Micrel, IncorporatedInventors: William A. Burkland, Jonathan Crandall
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Publication number: 20100052735Abstract: A level shifter circuit includes two parallel current paths respectively controlled by switch transistors, a Wilson current mirror circuit, and a slew rate control circuit to selectively couple an output node either to a high (first) voltage source or to a ground (second voltage) source in response to differential input control signals signal. When the output node reaches a stable (high or low) voltage level, the low voltage on one of the current paths turns off a Wilson current mirror transistor in the other current path, thereby preventing quiescent current during stable periods. An optional cascode transistor is added to facilitate fabrication using low threshold voltage transistors.Type: ApplicationFiled: August 28, 2008Publication date: March 4, 2010Applicant: Micrel, IncorporatedInventors: William A. Burkland, Jonathan Crandall
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Publication number: 20070071048Abstract: An accelerator circuit is incorporated in a laser diode system for accelerating the turn-on operation of the laser diode independent of the control loop bandwidth of the laser diode system. The accelerator circuit provides a boost current to a compensation capacitor upon laser turn-on which compensation capacitor operates to establish the control loop bandwidth of the laser diode system. The boost current enables the control loop to increase the bias current to the laser diode quickly. When the laser diode reaches the desired operating point, the boost current is terminated and the control loop of the laser diode system resumes normal control of the bias current. In one embodiment, the accelerator circuit includes a timer circuit controlling a current source to implement open loop turn-on control. In another embodiment, the accelerator circuit includes a comparator circuit working in conjunction with an one-shot logic circuit for providing close loop control.Type: ApplicationFiled: November 13, 2006Publication date: March 29, 2007Applicant: Micrel, Inc.Inventors: Douglas Anderson, Peter Chambers, Joseph Judkins, William Burkland
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Publication number: 20060244545Abstract: A timer circuit includes a current mirror, a capacitor, a first switch, a resistor and a comparator. The current mirror receives a reference current and provides first and second currents with a predefined current ratio. The capacitor receives the first current as a sinking current or as a sourcing current. The first switch, controlled by a control signal, allows the capacitor to be charged by the first current or be discharged. The resistor is biased by the second current to provide an adaptive reference voltage. The comparator compares the voltage across the capacitor and the adaptive reference voltage and triggers an output signal when the capacitor voltage is increased to the adaptive reference voltage.Type: ApplicationFiled: July 13, 2006Publication date: November 2, 2006Applicant: MICREL, INC.Inventors: Boris Briskin, William Burkland
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Patent number: 7075373Abstract: An overcurrent protection circuit for a power transistor includes a transconductance amplifier and a bias current circuit. The transconductance amplifier receives a first signal indicative of the magnitude of the load current conducted by the power transistor and a reference voltage and provides a second signal for controlling the load current. The transconductance amplifier further provides a third signal having a first logical state indicating normal operation and a second logical state indicating an overcurrent condition at the power transistor. The bias current circuit provides an output bias current to the transconductance amplifier in response to the third signal where the output bias current has a nominal current value in normal operation and an increased current value in an overcurrent condition. In this manner, a boost current is provided to the transconductance amplifier to increase the current limit response time when an overcurrent condition is detected.Type: GrantFiled: November 2, 2004Date of Patent: July 11, 2006Assignee: Micrel, Inc.Inventors: Boris Briskin, William A. Burkland
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Publication number: 20060091961Abstract: An overcurrent protection circuit for a power transistor includes a transconductance amplifier and a bias current circuit. The transconductance amplifier receives a first signal indicative of the magnitude of the load current conducted by the power transistor and a reference voltage and provides a second signal for controlling the load current. The transconductance amplifier further provides a third signal having a first logical state indicating normal operation and a second logical state indicating an overcurrent condition at the power transistor. The bias current circuit provides an output bias current to the transconductance amplifier in response to the third signal where the output bias current has a nominal current value in normal operation and an increased current value in an overcurrent condition. In this manner, a boost current is provided to the transconductance amplifier to increase the current limit response time when an overcurrent condition is detected.Type: ApplicationFiled: November 2, 2004Publication date: May 4, 2006Inventors: Boris Briskin, William Burkland
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Publication number: 20060082394Abstract: A timer circuit includes a current mirror, a capacitor, a first switch, a resistor and a comparator. The current mirror receives a reference current and provides first and second currents with a predefined current ratio. The first switch, controlled by a control signal, allows the capacitor to be charged by the first current or be discharged. The resistor is biased by the second current to provide an adaptive reference voltage. The comparator compares the voltage across the capacitor and the adaptive reference voltage and triggers an output signal when the capacitor voltage is increased to the adaptive reference voltage. Alternately, the timer circuit includes a pin for coupling to an external resistor and an open pin detector circuit to detect the presence of the external resistor and to automatically select the adaptive reference voltage if a resistor is present or an internal reference voltage if the resistor is absent.Type: ApplicationFiled: October 18, 2004Publication date: April 20, 2006Inventors: Boris Briskin, William Burkland
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Patent number: 6954160Abstract: A filter is described for digitally processing an analog input signal with analog feedback. In one example, the filter uses a topology similar to a second order universal filter block and includes a signal combiner for producing an analog output signal based upon an analog input signal and one or more analog feedback signals. An analog to digital converter processes the analog output signal into a digital data stream which is digitally processed to produce one or more digital output signals which are converted to one or more analog feedback signals. The digital processing can include a bandpass transfer function and a lowpass transfer function. The filter may be implemented in mixed-signal CMOS using standard CMOS processing techniques.Type: GrantFiled: April 9, 2004Date of Patent: October 11, 2005Assignee: Micrel, Inc.Inventors: William A. Burkland, Jonathan S. McCalmont
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Publication number: 20050129075Abstract: An accelerator circuit is incorporated in a laser diode system for accelerating the turn-on operation of the laser diode independent of the control loop bandwidth of the laser diode system. The accelerator circuit provides a boost current to a compensation capacitor upon laser turn-on which compensation capacitor operates to establish the control loop bandwidth of the laser diode system. The boost current enables the control loop to increase the bias current to the laser diode quickly. When the laser diode reaches the desired operating point, the boost current is terminated and the control loop of the laser diode system resumes normal control of the bias current. In one embodiment, the accelerator circuit includes a timer circuit controlling a current source to implement open loop turn-on control. In another embodiment, the accelerator circuit includes a comparator circuit working in conjunction with an one-shot logic circuit for providing close loop control.Type: ApplicationFiled: January 15, 2004Publication date: June 16, 2005Inventors: Douglas Anderson, Peter Chambers, Joseph Judkins, William Burkland