1996-02-01

Single Chip Power System for Engine Controllers 960332

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. These regulators will track a reference voltage such as the A/D's power supply within +/-10mV over all temperature and load conditions eliminating system gain errors and provides fault isolation between sensors. The combination of enable/disable hysteresis and power-on reset with a 20mS delay ensures well orchestrated, glitch-free power sequencing of the microprocessor. To meet all automotive requirements (temperature, voltage, etc.), this system on a chip maintains full performance during 50V load dump, provides 4KV ESD protection to all pins and has short circuit protection on all outputs.

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