EMI Design Techniques for Microcontrollers in Automotive Applications

EMI Design Techniques for Microcontrollers in Automotive Applications

ABSTRACT

Electronic contents of automobiles and other vehicles has grown rapidly in recent years. Embedded microcontrollers are used in a wide range of vehicle applications for control, convenience, and comfort Examples range from sophisticated engine and braking controls to automated radios and individual passenger temperature controls.

As the electronics content of vehicles have increased, so have the electromagnetic interference (EMI) problems. These range from annoyances (jamming an on-boardAM of FM radio) to upset or damage (blowing out an engine control module due to power transients.) The problems are expected to get worse as system clock speeds and logic edge rates increase, due to increased EMI emissions and decreased EMI immunity.

This application note describes the automotive EMI environments, and then discusses how to identify and prevent many common EMI problems at the design stage. Although a range of solutions will be addressed, emphasis is on printed circuit board design methods.

This application note also describes some recent Intel sponsored research efforts that investigate EMI to onboard FM radio receivers. Several different design approaches were tested, using both two layer and multiplayer circuit boards. The test program was based on an ABS (anti-lock braking system) control module that uses the Intel 80C196KR microcontroller. The results and recommended “low noise” design concepts, however, apply to any microcontroller design used in vehicular applications.