Motorola Corporation

Brian D Chapman

Jeffrey P Kotowski

Sang Hoon Kim

Kevin M Andrews

A power supply system (300) provides a staged startup of multiple loads (303, 305). Preferably, the power supply (300) is a switching power supply that provides power, in the form of a primary output voltage to a first output terminal (319) and to a second output terminal (325). A first load (303) demands a first startup power from the switching power supply through the first output terminal (319). A voltage comparator (333) provides an enable signal (335) when a primary output signal, present at the first output terminal, exceeds a predetermined threshold (335). A load coupling device, preferably a gateable voltage regulator (331), is coupled to the second output terminal (325). The gateable voltage regulator (331) has an output (327) coupled to a second load (305). The gateable voltage regulator (331), responsive to the enable signal (335), provides a coupling between the second output terminal (325) and the second load (305), whereby the second load (305) demands a second startup power from the power supply through the second output terminal (325).

Power supply distributed load startup system

A driver circuit (10), with a minimum number of interconnects between itself and a conventional output driver device (14), controls the normal on/off operation of the output driver device, and additionally senses various fault conditions within the output driver device. The driver circuit (10) also preferably shuts down the output driver device when the latter device begins to operate in a current limiting mode, and generates diagnostic signals which identify the type of fault condition that is sensed.

Fault sensing and driving system for output driver device

Overvoltage protection circuit (10) has a power transistor (11) that drives an inductive load (19). A resistor (16) is connected between an output electrode (14) of the transistor and a control electrode (12) of the transistor, and a constant current source (18) is also connected to the control electrode. The resistor and constant current source determine an effective zener voltage to limit the maximum voltage which can exist at the transistor output electrode (14), and this is accomplished without the use of a zener diode while utilizing a minimum number of components. This effective zener diode voltage can be readily adjusted by adjusting either the magnitude of the resistor (16) or the constant current source (18).

Overvoltage protection circuit

A transistor sense electrode (20) is coupled to the input branch (24) of a current mirror (22). The current mirror's branch (26) carries a current substantially equal to the current in the input branch to indicate the current flowing in the transistor. A preferred embodiment includes an amplifier (30) which senses the difference between the voltage at the sense electrode (20) and a reference voltage (Vx). The sensed difference in voltage causes the amplifier to apply a control signal to the current mirror to vary the current in the input branch so as to hold the sense electrode's voltage at the level of the reference voltage (Vx). A preferred package for the system's circuitry is also disclosed.

System for sensing and/or controlling the level of current in a

A method and apparatus is disclosed for measuring and/or controlling the level of current in a Sense FET which includes a power transistor (M1) and a sense transistor (M2). The transistors (M1) and (M2) are both biased to operate in a linear mode, and the Vds of the sense transistor (M2) is compared to a predetermined fraction of the Vds of the power transistor (M1). A control signal is generated that is representative of the results of the comparison, and, in one embodiment, that control signal is used in a feedback arrangement to drive the Vds of the sense transistor (M2) to the predetermined fraction of the Vds of the power transistor (M1). Consequently, the level of current carried by the sense transistor (M2) is caused to be equal to the same predetermined fraction of the current carried by the power transistor (M1).

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Gurnee, IL, United States of America

Brian D Chapman