Motorola Corporation

Arthur J Edwards

Randall C Gray

Kirk A Sievers

Philippe B Bauser

Adelore F Petrie

Steven G Parmelee

Mihaly Lamoth

Thomas F Karlmann

Nicholas Lee

A current-controlled differential input comparator having a double sided hysteresis is provided, including a differential input comparator having a first comparator input, a second comparator input, a comparator output, and a switching threshold, wherein the switching threshold causes the comparator output to have a first output state when the first comparator input is greater than the second comparator input and to have a second output state when the first comparator input is less than the second comparator input, a first hysteresis resistor communicating with the first comparator input, a second hysteresis resistor communicating with the second comparator input, an inverter connected to the comparator output, the inverter generating an inverted comparator output, and a current supply connected to the comparator output and to the inverted comparator output, the current supply being capable of switching a first hysteresis current to the first hysteresis resistor and a second hysteresis current to the second hysteresis resistor, wherein the double sided hysteresis is created by the first hysteresis current flowing through the first hysteresis resistor and by the second hysteresis current flowing through the second hysteresis resistor.

Differential input comparator with double sided hysteresis

A programmable amplitude ramp generator for an automotive voltage regulator includes a selection circuit (405) with an output (406) that provides a selection signal (407) with a plurality of states. A voltage reference circuit (401, 403) includes an output (410) that provides a different reference voltage dependent on each of the plurality of states of the selection signal (407). A resistive device (411) has an input (414) coupled to the output (410) of the voltage reference (401, 403), and an output (416). A gateable multi-resistive device (413) has an output (415) coupled to the output 416 of the resistive device 411. A coupleable resistive device (409) has an input (419) coupled to the output (410) of the voltage reference circuit (401, 403) and an output (421) coupleable to the output (416) of the resistive device (411) responsive to receipt of one of the plurality of states of the selection signal (407). A regulator load driving circuit (113, 109, 107, 105, 124) is coupled to the output () of the voltage reference circuit (401, 403). The described structure provides a multi-range operating capability for the automotive voltage regulator.

Programmable amplitude ramp generator for automotive voltage regulators

A dual output temperature compensated voltage reference includes a voltage reference circuit (201) having a first output (203) for providing a first signal (204) dependent on temperature, and a second output (207) for providing a second signal (208) dependent on the first signal (204). A temperature dependence of the first signal (204) has a slope opposite a temperature dependence of the second signal (208). A cooperative device (209), such as a resistive divider (309, 311), combines the first and second signals (204, 208) and provides a third signal (212) dependent on the first and second signals (204, 208). Preferably, this apparatus is applied in a charge regulator including fault detection (109). The charge regulator (109) generates a charge voltage (110) dependent on the first signal (204) and a fault detection function is dependent on the third signal (212).

Dual output temperature compensated voltage reference

A phase winding detector (50) is preferably used to detect alternator (11) rotation in an alternator charging system (10). The detector (50) receives a single winding phase output signal (at 39) and utilizes a sampling apparatus (71, 74, 76) to provide a sampled phase output signal (at 75). A comparison circuit (70) provides an output by comparing the phase output signal with the sampled phase output signal, whereby a detection of variation in the phase output signal is provided (at terminals 85, 87 and 51). After initial detection of variation of the phase winding output signal, preferably additional circuitry (77, 79, 83) results in comparing the phase winding signal with a fixed reference threshold (V.sub.ref). Detection of a phase winding output signal is implemented without use of a substantial DC blocking capacitor and is implemented by monitoring only one input signal terminal.

Phase winding detector and alternator charging system

A thermally dependent self-modifying voltage source (115) is constructed with a first reference circuit (301) having a control input (311), a primary output (117) dependent on the control input, and a thermally dependent secondary output (303). The thermally dependent self-modifying voltage source also includes a thermally dependent reference (309) with an output (307). The thermally dependent secondary output (303) of the first reference circuit (301) and output (307) of the thermally dependent reference (309) are coupled to inputs of an amplifier (305). The amplifier (305) has an output (313) coupled to the control input (311) of the first reference circuit (301), wherein the primary output (117) of the first reference circuit is dependent on the amplified difference between the thermally dependent secondary output (303) of the first reference circuit and the output (307) of the thermally dependent reference (309). Preferably, the primary output (117) is used in a voltage regulator (121) for use in alternator based battery charging system (100).

Thermally dependent self-modifying voltage source

In a circuit for overvoltage protection of a low voltage device (11) arranged to control a load (12) an energy storage capacitor (17) is connected to charge from supply (+V) while the device is controlled from a control circuit (100). During overvoltage, the controller is disconnected by switch means (15) and capacitor connected by switch means (16, 18) across the device to maintain it in an on state so that overvoltage device damage is prevented. The circuit is suited to transitory overvoltage conditions such as automotive load dump and to integration with the controlled device.

Circuit for overvoltage protection

A method for establishing a test mode in an electronic module (10) having an internal fault detector (26) that limits the current in an output transistor (Q1) when an abnormal signal level appears at an output pin (16). An abnormal signal level is intentionally established on the output pin to enable the fault detector, and such enablement is sensed to trigger the test mode within the module. Apparatus for implementing this method in a voltage regulator is also disclosed.

Enablement of a test mode in an electronic module with limited pin-outs

A driver circuit for driving from the same output node (6) an inductive relay (34) and a non-inductive lamp (30) having a transistor (16) for driving the relay and second transistor (18) for driving the lamp and a third transistor (90) having its current electrodes coupled between the control electrodes of the first and second transistors for sensing an inductively-induced voltage at the output node when the first transistor means is disabled to cease driving the relay and for enabling the first transistor in response thereto to dissipate the inductively-induced voltage at the output node so as to protect the second transistor. Alternative couplings of the third transistor to the second transistor are also disclosed.

Inductive load driving circuit with inductively induced voltage

A circuit (2) for use with an automotive voltage regulator (16), having: an input node (4) for receiving an input voltage (V.sub.BAT); an output node (12) for producing a regulated output voltage (V.sub.REG); a control node (18) for receiving a control signal from the voltage regulator; a first transistor (10) having its emitter connected via a protection diode (6) to the input node, its collector connected to the output node, and its base connected to the control node; an electrolytic input capacitor (8) connected between the first transistor emitter and ground; an electrolytic output capacitor (14) connected between the output node and ground; and a second transistor (32) having its emitter connected to the input node, its collector coupled to the output node, and its base for coupling to the voltage regulator. The second transistor allows the circuit to provide regulation at a lower input voltage, while retaining the protection diode. The circuit may be fabricated in integrated circuit form, possibly including the voltage regulator.

Circuit for use with a voltage regulator

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.

Voltage-clamped integrated circuit

A switchable filter has characteristics (e.g., time constant) that are changed by a low offset, bipolar switch that is turned off and on to periodically connect/disconnect an additional circuit element to the filter. The preferred embodiment is specially designed for use in an automotive voltage regulator.

Switched filter with low offset

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.

Floating output digital to analog converter

A bi-level control signal is applied to an FET while the FET's drain-to-source voltage is sensed. The control signal includes a first, relatively low test level followed by a second, relatively higher operating level. The magnitude and duration of the test level are selected to produce a non-destructive current in the FET, even if the load has been shorted. If the value of the sensed drain-to-source voltage is indicative of an abnormal load condition, the FET is turned off. Otherwise, the FET is turned on by the second, relatively higher operating level of the control signal.

Protective, bi-level drive for FET's

An interface circuit serves to rectify excitation energy inductively coupled to a transistor acting in a diode configuration to charge a reservoir capacitor which may then serve as a power source. Switch means under the control of an external functional circuit block is arranged to bias the transistor into a reverse operating mode to itself act as a switch to discharge energy from the reservoir into the coupling. In this way pulses may be back coupled to be detected at the excitation source. The timing of the back coupled pulses may be information bearing.

Power and signal transfer interface circuit

Semiconductor device protection circuit (10) provides increased power dissipation (current) limits for FET (11) when lower FET temperatures exist. The FET drain to source voltage (V.sub.DS) is monitored to provide a current sense signal (54). When the current sense signal exceeds a predetermined reference limit signal (V.sub.REF,55), a control circuit (23, 32) reduces current (power dissipation) in the FET. Circuitry (24) provides the reference limit signal (V.sub.REF) with a predetermined temperature variation as a function of the sensed temperature of the FET whereby for low device temperatures higher power dissipation (current) limits for the FET are provided. An additional control circuit (21, 30) provides short circuit overcurrent protection by reducing current in the FET when sensed FET current exceeds a predetermined limit. A delay circuit (39) inhibits operation of at least the control circuit (20, 32) until a predetermined time (t.sub.1) after the FET is turned on.

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Hoffman Estates, IL, United States of America

Arthur J Edwards