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The U552 is a single chip, switched mode power supply (SMPS) for automotive engine controllers. It is a complete power supply for microprocessor based systems and includes several support functions to provide improved efficiency, higher reliability, size reduction, decreased parts count and significant cost savings over other implementations. The current mode SMPS runs at 100KHz via an on chip oscillator with an accuracy of +/-10%. Noise suppression and supply rejection are achieved by powering all linear and digital blocks from an internally pre-regulated 5V supply. A precision reference provides 2% output voltage accuracy from -40 to +150 degrees C. Connected directly to the battery, a low quiescent current, stand-by regulator powers SRAM containing on-board diagnostics (OBD). Two 100mA, linear tracking regulators are on chip to drive sensors such as manifold absolute pressure (MAP) and throttle position.

Accurate knowledge of crank angle is essential to the correct operation of both ignition and fuel injection systems, yet the interface is one of the most problematic in a fuel injection system. The problems are well known to car manufacturers, but for many small engine manufacturers they are yet to be encountered. This paper describes a semiconductor circuit solution as integrated into the MC33813 and MC33814 Application Specific ICs for small engines. A circuit has been developed that uses the mathematical properties of VR sensor signals to create a robust interface that makes the fewest possible mistakes in the counting of crank position teeth. Validation pictures show a high level of noise immunity thus demonstrating suitability for the variation present in high volume manufacturing.