Motorola Corporation

Paul Moraghan

Roy E Hunninghaus

Eugene L Wineinger

Gregory A Kujawa

A current through a transistor having a drain and a source is sensed using a resistor, and first and second current sources. The resistor is responsive to the first current source to establish a reference voltage between a first terminal and a second terminal. The second terminal of the resistor is coupled to the source of the transistor. The second current source is current-controlled by the first current source and has a current gain inversely related to a voltage between the drain of the transistor and the first terminal of the resistor.

Power transistor current sensing and limiting apparatus

A solenoid driver (10) capable of detecting the operational status of a solenoid (12) including the position of an armature within a solenoid coil and an operational method. The solenoid driver (10) generates a first solenoid current within the solenoid (12) and measures a first decay time t.sub.1. The first solenoid current is insufficient to pull the armature into the coil of the solenoid (12). A comparator circuit (22) continuously monitors the solenoid current and initiates a timer within a counter circuit (34) to compute the first current decay time. A second solenoid current is generated within the solenoid (12) that is sufficient to pull the armature into the coil of the solenoid (12). The second solenoid current is turned off and a second decay time t.sub.2 is measured. The decay times are stored in storage registers (R1, R2) within a controller (36). The controller (36) compares the measured decay times with stored values and outputs the armature position information over a communications bus (34).

Solenoid driver and method for determining solenoid operational status

A low power consumption switch interface circuit (100) includes a current source (109) for providing switch current (144) having a magnitude dependent on a state of a current range signal (135). An input terminal (142) is provided to conduct the switch current (144) to an external switch (102). A circuit (101, 103, 119) for detecting a signal (141) present at the input terminal (142) provides a measured pulse (127) when the signal (141) is detected. A current range selector (129), coupled to the current source (109), outputs a first state of the current range signal (135) while the measured pulse (127) is outputted from the circuit (101, 103, 119), and a second state of the current range signal (135) while the measured pulse (127) is not outputted from the circuit (101, 103, 119). The current source (109) provides the switch current (144) at a first magnitude responsive to the first state of the current range signal (135), and a second magnitude responsive to the second state of the current range signal (135).

Growing community of inventors

Chicago, IL, United States of America

Paul Moraghan