Abstract: A sensing circuit for detecting open and short circuit conditions in sensors is provided. The sensing circuit includes switching circuitry, a voltage supply, a test capacitor, and an operational amplifier. The switching circuitry is electrically coupled to the voltage supply, test capacitor, operational amplifier, and a sensor. The sensing circuit is configured to provide for a normal operating mode in which the sensing circuit provides an output indicative of a voltage across the sensor, and a charging mode in which the test capacitor is coupled to the sensor and operational amplifier and charged to a steady state, and in which the output of the operational amplifier is a function of the test capacitor capacitance and the capacitance of the sensor. A method for detecting open and short circuit conditions in sensors is also provided.

Abstract: A sensor interface filter having adjustable gain and Q is provided. The sensor interface includes a first operational amplifier coupled to gain circuitry, a gain stage, and a resistor. The gain circuitry and gain stage are electrically coupled to each other. The gain stage includes a gain stage switch, and is coupled to control circuitry. The control circuitry controls the state of the gain stage switch to vary the number of feedback current paths providing feedback to the inverting input of the first operational amplifier, altering the gain provided by the first operational amplifier. The sensor interface further includes a second operational amplifier coupled to filter circuitry and feedback switches. The feedback switches are coupled to the control circuitry, which controls the state of the feedback switches to vary the gain provided by the second operational amplifier and the filter Q of the sensor interface. A method is also provided.

Abstract: A sensor interface filter having adjustable gain and Q is provided. The sensor interface includes a first operational amplifier coupled to gain circuitry, a gain stage, and a resistor. The gain circuitry and gain stage are electrically coupled to each other. The gain stage includes a gain stage switch, and is coupled to control circuitry. The control circuitry controls the state of the gain stage switch to vary the number of feedback current paths providing feedback to the inverting input of the first operational amplifier, altering the gain provided by the first operational amplifier. The sensor interface further includes a second operational amplifier coupled to filter circuitry and feedback switches. The feedback switches are coupled to the control circuitry, which controls the state of the feedback switches to vary the gain provided by the second operational amplifier and the filter Q of the sensor interface. A method is also provided.

Abstract: A sensing circuit for detecting open and short circuit conditions in sensors is provided. The sensing circuit includes switching circuitry, a voltage supply, a test capacitor, and an operational amplifier. The switching circuitry is electrically coupled to the voltage supply, test capacitor, operational amplifier, and a sensor. The sensing circuit is configured to provide for a normal operating mode in which the sensing circuit provides an output indicative of a voltage across the sensor, and a charging mode in which the test capacitor is coupled to the sensor and operational amplifier and charged to a steady state, and in which the output of the operational amplifier is a function of the test capacitor capacitance and the capacitance of the sensor. A method for detecting open and short circuit conditions in sensors is also provided.

Abstract: A circuit for converting an analog signal to a PWM signal samples an amplitude of the analog signal at first sampling rate and a second slower sampling rate, and produces corresponding first and second signals. A comparison signal defines a first state when the first signal is greater than the second signal, and otherwise defines a second opposite state. The PWM signal switches from a first signal level to a second signal level when the comparison signal switches from the first state to the second state only if the comparison signal thereafter remains in the second state for a specified delay period, and the PWM signal switches from the second signal level to the first signal level when the comparison signal switches from the second state to the first state only if the comparison signal thereafter remains in the first state for the delay period.

Abstract: A digital equivalent of a periodic analog signal is generated in a manner substantially insensitive to variations in the reference about which the analog signal oscillates by switching the digital equivalent between high and low levels based on reference voltages derived from the peaks and valleys of the analog signal. The manner of generating the digital equivalent is substantially insensitive to common mode noise across the analog signal generator by locking a differential signal output when significant common mode noise in sensed. Generator faults are also diagnosed.

Abstract: A motor driver interface (MDI) circuit includes fault detection apparatus effective to detect short circuits to the power supply in the switching transistors of an H-bridge reversible DC motor arrangement. A pair of timers distinguishes a true fault condition. The first timer is responsive to a continuous fault detection to define a first time period from its initiation; and a second timer is responsive to a continuous presence of a transistor conduction signal to define a second time period from its initiation. The apparatus stores a fault signal in response to the detection of the fault condition at the end of the first or second time periods with the first timer providing fault detection upon turn-on after the brief initial high transistor turn-on current and the second timer providing noise immunity.

Abstract: A motor driver interface (MDI) circuit for an H-bridge electric motor drive apparatus is responsive to an enable signal to turn off all switching transistors in a not enabled mode and turn on the upper bridge transistors in an enabled mode and includes large resistors, sufficiently large to prevent motor activation therethrough, from the motor terminals to the power supply terminals to establish a bias voltage in the not enabled mode. Fault detection apparatus compares the voltages at the motor terminals with a first reference voltage apparatus in the not enabled mode and a second reference voltage apparatus in the enabled mode in response to the enable signal.

Abstract: A control for an inductive load switches current on and off to regulate about a command value, a decaying recirculation current flowing through the load during the switch off periods. The current is sensed during the switch on periods and charges a capacitor to provide a simulation signal representing the motor current. The capacitor is allowed to discharge through a resistor during the switch off periods at the rate of the decaying recirculation current. The simulation signal is compared to the command value to control the switching. The simulation signal is sensed during a command value of zero current to determine offset errors for calibration purposes.

Abstract: An interface circuit between a microcomputer and a MOSFET driver for motor control includes logic for failsafe motor control particularly to protect the driver. AND gates supply driver signals when a set of conditions are met. Certain conditions are mandated directly by the microcomputer. An analog oscillator and digital counter are used to time data signals from the microcomputer to assure continual computer operation. Other conditions are determined by the logic and include monitoring faulty motor current conditions, assuring that forward and reverse signals are not given concurrently, and assuring that there is a dead time between forward and reverse signals to the driver.