Abstract: An overvoltage protection circuit (11) for decoupling circuitry (12) from a voltage applied to an input (38). The overvoltage protection circuit (11) is integrated on an integrated circuit along with the circuitry (12). The overvoltage protection circuit (11) comprises a sense circuit (13), a timing circuit (14), a decoupling circuit (16), and a circuit (17). The sense circuit (13) detects when the voltage applied to the input (38) exceeds a threshold voltage. The timing circuit (14) is responsive to the sense circuit (13) and determines when the voltage exceeds the threshold voltage for a predetermined time. The decoupling circuit (16) is responsive to the timing circuit (14) and decouples the circuitry from the voltage applied to the input (38). The circuit (17) generates a logic signal indicating the circuitry has been decoupled.

Abstract: An oscillator circuit with enhanced frequency characteristics is provided. This oscillator circuit includes a buffer (102) to amplify the output signal and provide a positive feedback, an inverter (106) to provide negative feedback to cause oscillation, a capacitive divider circuit (110, 112) for charge storage, a resistor (116) to provide controlled discharge, and a diode circuit (114) for providing frequency stability. Since frequency stability is included within the oscillator circuit, there may be no need to perform resistor trimming at the time of manufacture. Further, the capacitive divider circuit eliminates parasitic charge injection.

Abstract: A two stage gate drive circuit (10) for controlling a power transistor (12) has been provided. The drive circuit includes a first stage (14) coupled to a first supply voltage terminal for providing a high current drive signal to the power transistor for quickly switching on the power transistor. However, once the power transistor is turned on, the first stage becomes inactive and a second stage (16) coupled to a second supply voltage terminal provides a low current drive signal to the power transistor for fully enhancing the power transistor and lowering its on resistance. The gate drive circuit further includes a timer circuit (18) for rendering the first stage active for predetermined period of time.

Abstract: A slew rate limited load driver is disclosed with a transistor switch (123) driving a load (125). The transistor switch (123) is controlled by a current from a current amplifier (107) and a current sink (111). The current amplifier (107) is driven from the combination of a source of compensating current (120) and a turn on current source (115). As a command signal (103) transitions, the source of compensating current (120) adds a transitional compensating current to the current derived from the turn on current source (115) and is amplified by the current amplifier (107). The output of the current amplifier (107) is combined with the output of the turn off current sink (111), to control the voltage slew rate to the load (101).

Abstract: An automobile alternator regulator integrated circuit having a voltage-supply or -sense node (6) for connection to an external voltage, and a voltage clamp comprising: a pnp bypass transistor (Q1) having a base electrode, an emitter electrode coupled to the node and a collector electrode coupled to ground; a resistor (R1) connected between the base electrode and the node; a Zener diode (Z1-Z4) connected between the base electrode and ground for enabling the bypass transistor when the voltage at the node exceeds a predetermined value, whereby the voltage at the node is clamped to a voltage no greater than the predetermined value; and a fuse (F1) connected between the node and the emitter electrode so as to provide a subsequently identifiable cause of failure if the fuse becomes blown due to excess voltage while allowing subsequent operation of the integrated circuit if the clamp means fails but another part of the integrated circuit remains functional.

Abstract: A digital to analog converter circuit produces an output voltage which includes a small error voltage floating on a larger direct current voltage component. The circuit includes a controlled current supply coupled to the emitter of an NPN transistor to which the direct current voltage component is supplied to the base thereof. The error voltage is generated by modulating the current through the transistor by controlling the current supply, independent of the voltage component supplied to its base, such that the output voltage occurring at the emitter of the transistor is a function of the difference between the direct current component and the natural log of the modulated emitter current.

Abstract: A regulator is responsive to an input signal proportional to the system supply voltage for adjusting the current flowing in the field windings of an electrical alternator which controls the output power thereof. The primary regulation loop of the regulator generates a pulse train having a duty cycle inversely proportional to the amplitude of the input signal while an oscillator provides a sawtooth signal at a predetermined frequency which controls the response frequency of the regulator. The regulator limits the rate of increase in the duty cycle of pulse train upon detecting a decrease in the system supply voltage by converting the duty cycle of the pulse train to a charging signal for developing a voltage across a capacitor proportional to the duty cycle of the pulse train. The voltage across the capacitor is compared to the sawtooth signal and triggers a latch which disables the output signal of the regulator as the duty cycle lengthens in response to the decrease in the system supply voltage.

Abstract: A regulator for a vehicle charging system senses when it applies and terminates excitation to the field winding of the charging system's alternator. When the excitation is applied to the field windings, the output of the alternator is connected to an input filter in the regulator so that the regulator can sense the alternator's output. When the excitation is terminated, the input filter is disconnected from the alternator's output to isolate the filter from voltage steps induced in the alternator's output by the turn-on and turn-off of the field excitation.

Abstract: A MOS differential to single ended converter circuit is provided for supplying a single ouput signal in response to first and second differentially related current being supplied to first and second junctions thereof. The converter circuit includes first and second MOS transistors each having gate, drain and source electrodes with the gate electrodes being coupled together while the drain and gate electrodes of the first transistor are interconnected. The drain and source electrodes of the pair of transistors are respectively coupled in series with the first and second junctions. First and second bipolar transistors each having first, second and control electrodes are provided for limiting the voltage swing at the drain of the second MOS transistor.

Abstract: Integrated circuit voltage regulator (60; 81; 91) is provided for use in a battery charging system (10) for providing excitation current to a field coil (13) of an alternator (11). The integrated circuit voltage regulator includes a transistor (70) which is selectively switched on and off to implement the prior art diesel diode (26) functions of providing initial field coil excitation current while preventing undesired current flow from an alternator voltage supply terminal (20) during subsequent field coil excitation current. The transistor (70) is provided as part of an integrated circuit and, therefore, eliminates the need for a diesel diode (26) external to the integrated circuit. In addition, use of the switched transistor (70) minimizes voltage drop loss when providing initial field excitation current. Constructing the transistor (70) as a PNP vertical substrate transistor minimizes integrated circuit area and simplifies integrated circuit topology.

Abstract: In a solenoid fuel injection system, an output transistor (16) receives switching signals to control through current therein which is provided to a solenoid fuel injection coil (11) in series with a current sensing resistor (17). A current control circuit (12) provides pulse width modulation control of solenoid current by monitoring the voltage across the sensing resistor. The fault detection circuit provides separate fault signals for short circuits at either the first or second end terminals (E, H) of the solenoid coil. Separate voltage comparators (18, 23) monitor voltages at the first and second end terminals, and separate delay timers (20, 25) effectively gate the comparator outputs to indicate actual detected short circuits. Each of the fault detection signals sets a fault latch (22) which then acts to reduce current through the output transistor and coil. The fault latch is periodically reset.

Abstract: An improved solenoid driver control circuit is disclosed in which solenoid current is sensed and provided as an input to a comparator means comprising two separate comparators (24, 25). The comparator means receives a solenoid current sense signal (45) and maximum and minimum reference threshold levels which determine maximum and minimum current limits (I.sub.max, I.sub.min ; H.sub.max, H.sub.min) for solenoid current during initial pull-in excitation and subsequent hold excitation. Pull-in time (T.sub.1) is defined by a monostable multivibrator (33) reacting to a control pulse (41) to produce a predetermined pull-in time pulse (43) such that the pull-in time is independent of sensed solenoid current. During pull-in time a boost driver switch (53) applies high boost voltage to a power source terminal (16) which supplies solenoid current, and in response to achieving the maximum pull-in current limit (I.sub.max) lower battery voltage is provided at the power source terminal.

Abstract: A differential amplifier operated as a voltage comparator includes first and second transistors coupled to first and second inputs respectively of the comparator whereby an applied input signal produces output transitions at an output of the differential amplifier as the input signal passes through and exceeds a first threshold voltage established at the second input of the differential amplifier. A hysteresis producing circuit is coupled to the differential amplifier which is responsive to the applied input signal exceeding the first threshold voltage for establishing a second threshold voltage, which is less than the first threshold voltage, whereby the input signal has to decrease below the value of the first threshold voltage to the second threshold voltage in order for the differential amplifier to switch back to its original operating state wherein hysteresis is established.

Abstract: An improved comparator circuit of the type which includes first and second differential PNP transistors operating in conjunction with a current mirror circuit includes an additional dual collector PNP transistor. That is, while the reference voltage is applied to the base of one of the differential transistors, the input voltage to be compared with the reference voltage applied to the emitter of the dual collector's transistor which has a first collector coupled to the base of the other differential transistor. The second collector is coupled to the base of the additional transistor. In this manner, should the input voltage fall below the substrate voltage, the additional transistor will be reverse biased thus preventing the parasitic diode at the base of the second differential transistor from turning on.

Abstract: A circuit for detecting a very large output current threshold with respect to a flow reference current. The threshold detector circuit includes a multiple transistor circuit wherein a pair of emitter areas are ratioed with respect to each other, and which have common bases, and an error amplifier the inputs of which are connected to the respective emitters of the multiple transistor circuit. An output current is sourced from the emitter of the multiple transistor circuit having the larger area which output current is a function of the load coupled therewith to thereby produce a voltage at this emitter the magnitude thereof being a function of the output current.

Abstract: A short detection circuit and method for operatively controlling current in an electrical load such as an alternator field coil includes a driving device such as a Darlington transistor for driving the electrical load. Detecting means selectively withhold and provide operating current to the driving means when a shorted and not shorted condition of the electrical load is respectively detected at the driven terminal of the driving device.

Abstract: In a zener referenced voltage threshold detector, the voltage at which a switching transistor turns on is determined by the breakdown voltage of a zener diode coupled between ground and the base of the switching transistor in conjunction with the base-emitter voltage of the switching transistor itself. In order to render the threshold detector circuit immune from noise at the trip point, a portion of the switching transistor's collector current is supplied to a second transistor which when turned on reduces the voltage at the base of the switching transistor.

Abstract: A reference capacitor is coupled in parallel with a capacitor of which the size thereof is variable and an oscillator is used to alternately charge and discharge both capacitors between first and second voltage levels. The absolute magnitude of the current flowing through the reference capacitor, which varies in proportion to the size of the variable capacitor, is detected which is indicative of the variations in size of the variable capacitor. If the variable capacitor is disposed in the fuel tank of a vehicle, water in the fuel will cause the effective capacitance value of the capacitor to increase which reduces the absolute magnitude of the current that is detected. The absolute magnitude of the detected current can be utilized to indicate excessive water levels in the fuel.

Abstract: A variable temperature coefficient level shifter includes a circuit which generates a voltage V.sub.BE having a negative temperature coefficient and a voltage .DELTA.V.sub.BE having a positive temperature coefficient. A control current is generated by placing a first resistor between V.sub.BE and ground and a second resistor between .DELTA.V.sub.BE and ground. Each of these currents forms a component of the control current which then has some net temperature coefficient. By properly scaling the resistors the control current may have any desired temperature coefficient between 2800 ppm and 3000 ppm. Once the temperature coefficient is set, a third resistor is provided through which the control current flows. The amplitude of the shift is then selected by selecting the value of resistor R.sub.S.

Abstract: This relates to a circuit for delivering a linear voltage (V.sub.P) which is inversely proportional to the capacitance of a pressure sensitive capacitive transducer. A constant current I.sub.O is alternately switched into a reference capacitor (C.sub.R) and the transducer capacitor (C.sub.P). When the voltage across C.sub.P reaches V.sub.P, a flip-flop is toggled to direct current to C.sub.R. When the voltage across C.sub.R reaches a reference voltage (V.sub.R), the flip-flop is again toggled directing current to C.sub.P. A duty cycle detector charges integrator capacitors until the feedback voltage V.sub.P is such as to render equal the charging times of C.sub.P and C.sub.R.