Achieving ESD Equipment Protection with Emission Controls

Com m ercial com puters and o ffice equipment must be alm ost e rro r-free in the hostile e lec tro ­ m agnetic environments. The equipment will have to opera te reliably when placed within close proximity of major noise sources and powered by th e sam e mains supply. Power mains conduction and radiation lim its have been established by various regulatory agencies on emission sources to p ro tec t radio com­ m unications. However, these emission lim its do not insure error free operation amid all th e potentia l sources of noise. T herefore , each m anufacturer se ts his own noise im m unity standards based on cost e ffec tive designs. The main susceptib ility problem of com m ercial equipment is power mains conducted transien t susceptibility .il] The common and unusual transien ts sources have been characterized , and the expected transien t range of voltage and tim e param ­ e te rs have been described. The e lec tro s ta tic dis­ charges like lightning and from humans (commonly known as ESD) can be a problem if the product is not designed for these d ischarges.[2] This paper will dis­ cuss some aspects of the ESD phenomenon and the designing of equipment to pass a required ESD im munity level.