Motorola Corporation

Warren J Schultz

Robert Bruce Davies

Troy L Stockstad

Thomas D Petty

James J Stipanuk

Denise M Williams

Lloyd H Hayes

Herbert A Saladin

Jeffrey Baum

Stephen Su

An overcurrent detector circuit (21) for a power MOSFET (22) is described. The overcurrent detector circuit (21) generates a bias voltage corresponding to the drain to source voltage of the power MOSFET (22). The drain to source voltage correlates directly to the current being conducted by the power MOSFET (22). An overcurrent condition occurs when the power MOSFET (22) exceeds a predetermined current. The bias voltage is applied to a transistor (24) for generating a current. A current source (29) couples to the transistor (24). The current provided by the transistor equals the reference current of the current source (29) when the power MOSFET conducts the predetermined current. The overcurrent detector circuit (21) generates a signal indicating a overcurrent condition does not exist when the reference current is greater the current provided by the transistor. Conversely, the overcurrent detector circuit (21) generates a signal indicating the overcurrent condition when the current provided by the transistor exceeds the reference current.

Overcurrent detection circuit for a power MOSFET and method therefor

A large sense voltage is produced by the semiconductor device of the present invention. The semiconductor device, utilizing current mirror techniques, is comprised of a power MOSFET having a plurality of power cells and a plurality of sense cells formed in a semiconductor epitaxial layer. The large sense voltage is provided by isolating and separating the plurality of power cells from the plurality of sense cells by at least the thickness of the semiconductor epitaxial layer. Isolation can be provided by forming a plurality of inactive cells or an elongated cell between the plurality of power cells and the plurality of sense cells. In addition, high voltage capabilities can be maintained by including a partially active region adjacent the power cells to provide for good termination.

Semiconductor device having a large sense voltage

A pulsed pressure sensor circuit (11) with increased sensitivity for measuring low pressures. A pulse generation circuit (12) is enabled by a microprocessor (28) to output a voltage pulse. The voltage pulse biases a pressure sensor (17) which has a port exposed to a pressure to be sensed. The pressure sensor (17) outputs a differential voltage which is proportional to the pressure at the port. The differential voltage is amplified by an amplifier (23) which has an output coupled to the microprocessor (28). A voltage divider circuit (26) is coupled to the pulse generation circuit (12) and has an output coupled to the microprocessor (28). The microprocessor (28) samples the voltages at the output of the amplifier (23) and the output of the voltage divider circuit (26). Microprocessor (28) then calculates the pressure using the sampled voltages and data stored in memory.

Pulsed pressure sensor circuit and method therefor

A control circuit for switching AC or DC loads and for automatically discerning the presence of an AC or a DC power supply via a switch has been provided. The control circuit is coupled to alternately render a switch operative and non-operative wherein the switch is coupled across a load which is powered up by either an AC or a DC power supply. The control circuit includes an AC/DC discernment circuit for ascertaining whether the load is powered up by an AC or a DC power supply. The control circuit also includes circuitry for comparing signals sensed by the switch with predetermined thresholds (which are a function of whether an AC or DC determination has been made) for providing logic signals to control the operation of the switch.

Load control circuit including automatic AC/DC discernment

A circuit for a pulse width modulating a sensor (12) has been provided. The circuit includes a first switch (22) for alternately coupling the sensor between first and second supply voltage terminals. The circuit also includes second (24) and third (28) switches and first and second capacitors for sampling the differential voltage appearing at outputs of the sensor when the first switch is in a closed state.

Pressure sensor

A circuit for interfacing with the outputs of a differential pressure sensor provides a single-ended output voltage translated in voltage level with respect to the differential voltage applied thereto from the sensor while cancelling the common mode offset voltage of the sensor so that the output voltage is independent of the common mode offset voltage. The circuit includes four operational amplifiers arranged as a differential-to-single ended converter with gain.

Interface circuit

A normally non-conducting motor drive transistor is connected in parallel with a freewheeling diode. The transistor is briefly enabled while reverse recovery transition current is flowing in the freewheeling diode and thereby reduces noise created by the diode when it switches from conducting reverse recovery current to blocking reverse voltage.

Low noise motor drive circuit

A high voltage bridge interface circuit is provided for AC and brushless DC motor control having a high voltage isolation circuit and drive circuits which simplify the high voltage interface and reduce the total system integration effort. The isolation circuit provides the high voltage unilateral isolation between the control circuit and the high voltage power supply conductors, while the drive circuits improve the noise immunity at the gate termimals of the power MOSFET bridge. The high voltage bridge interface circuit is partitioned by providing the high voltage interface within one IC thereby permitting the integration of the discrete components of the power MOSFET drive circuits and simplifying the overall system integration.

High voltage bridge interface

A transformer coupled amplifier drive circuit (60) and method especially suited for providing a saw-tooth current waveform to an inductive load (32) for horizontal deflection applications in CRT monitors and the like are described. The transformer primary (48) is coupled between the power source connection (11) and the input of the amplifier (26) while the transformer secondary (50) has an opposite polarity terminal coupled to the input of the amplifier (26) through an inductor (52) and the other terminal of the secondary (50) coupled to the common terminal (15) of the amplifier (26) through a diode (56). When the input switch (44) is closed, the input of the amplifier (26) is energized by a current (65) through the series connected primary (48) and energy is stored in the transformer magnetizing field and in the amplifier (26). Conduction in the transformer secondary (50) is blocked by the diode (56). When the input switch (44) is opened, the input charging current (65) stops and the collapsing primary magnetizing field produces an oppositely directed current (67) which flows through the secondary winding (50), the diode (56), the series connected inductor (52) and the input to the amplifier (26). The demagnetization energy stored in the transformer (48) cancels the energy stored in the amplifier (26), thereby reducing total dissipation, and the inductor (52) controls the fall time independent of the rise time.

Amplifier drive circuit for inductive loads

An overvoltage and overtemperature protection circuit that includes an output thyristor fabricated in monolithic integrated circuit form is provided. The thyristor comprises a P-type substrate serving as an anode and diffused cathode and gate region wherein the current flows vertically, optimizing the high voltage and high current capability. A thermal limit circuit is provided for triggering the thyristor when a designated temperature is exceeded. The output thyristor will shunt the output voltage to ground whenever the predetermined voltage or temperature is exceeded.

Overvoltage and overtemperature protection circuit

A PWM controller for an electrical utilizes a dual differential input topology comprising two input comparators deriving a proportional reference from two potentiometers for providing a variable pulse width modulated output. The pulse width modulation controller of the present invention does not require scaling and may be utilized in appliances, robotics, toys and in conjunction with other electromechanical and electrical loads.

PWM controller for an electrical load

A semiconductor fuse is disclosed that provides protection against both overcurrent and the abrupt application of a voltage to semiconductor devices. A first means is coupled to an input terminal for providing a signal when a current is applied to the input terminal. A second means is coupled between the input terminal and an output terminal for allowing current to pass therebetween and is coupled to the detecting means and responsive to the signal. A third means is coupled between the output terminal and a ground terminal for shorting a current therebetween. A fourth means is coupled to the input terminal, the second means, and the third means for activating the third means and preventing the second means from responding to the signal when the input current exceeds a predetermined value.

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Tempe, AZ, United States of America

Warren J Schultz