Reducing electro-magnetic radiations with a multi chip module

The amount of electronic equipment loaded in cars is increasing. All parts of the vehicle are now driven by electronics, such as the engine control unit which manages the engine, or clutch and gear box systems which manage the car chassis, or, more recently, the alarm and navigation systems which manage the car body. Each generation of electronic equipment must be increasingly powerful, but at the same time the size must be reduced. Higher clock rates and data exchanges are good solutions for increased electronic equipment performance, but are bad for electromagnetic radiation. The use of multichip modules, with dice directly bonded to a small PCB, mixes the advantages of reduced hardware size for equivalent performance, a single package for several dice, and also to reduce the radiated electromagnetic field. This paper presents the differences in radiated emission levels between a microcontroller alone and a MCM using the same microcontroller with RAM and flash memory. The methodology used for the comparison according the American SAE 1752/3 standard is described. The test method used a TEM cell specially designed for component emission tests in the 150 kHz to 1000 MHz range. An analysis of the results allows identification of the different noise origins, such as the device core, clock systems and bus distribution. This also allows quantification of the gain of around 10 dB on radiated emission levels up to 1 GHz.