Microprocessor Based Systems in the Automobile: Custom Integrated Circuits Provide an Effective Interface

While the MOS microprocessor chip has been used as a cost effective electronic building block for simultaneously meeting the goals of fuel management, emissions and reliability, it has also created the need for additional interface electronics. Interface circuits are necessary to buffer and protect the sensitive MOS circuitry from the loading and electrical transients of mechanical switches, sensors, solenoids and indicators. In some instances, the interface can be solved using a few inexpensive discrete parts, but the complexity of new systems justifies the design of custom ICs to fulfill the requirements. This paper describes how custom bipolar ICs can be used to reduce system cost and improve noise immunity, as well as reliability, when designing interface electronics.