Stmicroelectronics S.r.l.

International Rectifier Corporation

Andrea Merello

Gianluca Ventura

Roberto Peritore

Marco Giandalia

Massimo Grasso

Alberto Salina

Aldo Torti

Giovanni Galli

Lorenzo Papillo

Jonas Aleksandravicius

Francesco Vavala

Current through a wire is sensed with a shunt resistor and a sense resistor in a current divider circuit. The values of the shunt resistor and sense resistor are related to provide a specified gain ratio to increase a dynamic range of current measurement. The sense resistor is a trimmable resistor, the configuration of which can be discerned from a look-up table based on a level of precision needed for current measurement. The two resistors can also be related by thermal coefficients to improve linearity of current measurements.

Current sense shunt resistor circuit

A gate drive integrated circuit for switching power transistors using an external controller includes a gate driving capability and low quiescent current and allows use of a bootstrap supply technique for providing the logic supply voltage. The gate driver integrated circuit detects power transistor desaturation, protecting a desaturated transistor from transient over voltages by smoothly turning off the desaturated transistor via a soft shutdown sequence. A fault control circuit of the gate driver integrated circuit manages protection of supply under-voltage and transistor desaturation and is capable of communicating with a plurality of gate driver integrated circuits in a multi-phase system using a dedicated local network.

Half-bridge high voltage gate driver providing protection of a transistor

A system for controlling and driving an electromagnetic actuator includes a unique operational amplifier in the regulation loop for driving the electromagnetic actuator and for monitoring, during different phases of operation, the current in the actuator and the back electromotive force. The new architecture allows for a considerable reduction of the area of integration of the system as a whole.

Control and drive system for a single winding electromagnetic actuator employing a single multifunction operational amplifier

The present invention relates to the positioning of the read/write transducer heads of an hard disk (HD) in a designated landing zone when requested or when the electrical power is removed from the drive. In particularly it relates to the detection of the back electromotive force (BEMF) of the motor involved in the positioning of the read/write transducer heads. According to an embodiment of the present invention a BEMF detection circuit for a voice-coil motor operative to continually generate a signal proportionally to the velocity of said voice-coil motor comprises a algebraic summing node producing at its output the BEMF of the voice-coil motor and receiving: a first voltage proportional to the voltage across the voice-coil motor; a second voltage representing the product of a first multiplier factor and a voltage proportional to the current in the coil; a third voltage representing the product of a prefixed bias voltage Vref and a second multiplier factor; said third voltage is calibrated by a single calibration circuitry operative to calibrate said second multiplier factor in response to a calibration control signal, in order to cancel said second voltage.

Calibration technique of a BEMF detector

A method for controlling an electromagnetic actuator having an arm connected thereto uses a circuit that temporarily places in a high impedance state output nodes connected to a winding of the electromagnetic actuator. A detected BEMF is compared with a lower threshold and an upper threshold. Current in the electromagnetic actuator is monitored and controlled. A current pulse is provided to the electromagnetic actuator based upon the comparison of the detected BEMF with the lower and upper thresholds. The respective amplitudes of successively provided current pulses having a same polarity are progressively increased, and an amplitude of a provided current pulse having a polarity opposite a polarity of a preceding current pulse is decreased. The amplitude of the driving current pulses provided to the winding of the electromagnetic actuator advantageously adapts automatically to varying frictional conditions, or to any other cause of variation of the mechanical load of the actuator. These conditions occur when the arm moved by the electromagnetic actuator starts to slide up or flies off the parking ramp.

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Arese, Italy

Andrea Merello