Electronic Design

Switch Chip Holds Promise For Automotive Power Apps

A new self-protected automotive-grade silicon switch offers solid-state reliability and power savings in power-management and load-control applications. Motorola's MC33982 ultimately could replace electromechanical relays, fuses, and discrete circuits in these applications. The high-side power switch combines two die—a highly configurable control circuit and a power MOSFET—in a 12- by 12-mm power QFN with a solderable die attach pad for heatsinking.

The FET's on-resistance is an extremely low 2 m‡. The switch protects against overcurrent, overtemperature, and negative battery. It also guards against overvoltage and undervoltage, ground disconnect, load dump transient, and open load. In addition, the IC has real-time fault status indication. Among its many programmable functions are output on/ off control, configurable overcurrent detection levels and blanking times for fuse emulation, and selectable output slew rate. The chip operates under direct microcontroller (MCU) control (see the figure).

At the recent Convergence2002 conference, Motorola demonstrated the part's high-current capabilities. The company combined eight MC33982s in parallel to create a solid-state replacement for the starter relay used on a V-6 engine. Even with two of the silicon switches removed from the circuit, the circuit could still supply the more than 750 A required to crank the engine. Though the starter relay is an unlikely application, other automotive applications like pump motors, blower motors, antilock braking systems, and lights are expected to benefit from the switch.

Pricing for the MC33982 is $3.90 each in quantities of 10,000. Samples are available now.

Motorola, www.motorola.com/semiconductors.

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