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Maxim > Design Support > Technical Documents > Application Notes > Automotive > APP 651
Maxim > Design Support > Technical Documents > Application Notes > Interface Circuits > APP 651
Maxim > Design Support > Technical Documents > Application Notes > Protection and Isolation > APP 651
Keywords: ESD protection, ESD, electrostatic discharge, human body model, machine model, IEC 1000-
4-2, 15kV, air discharge, contact discharge, triboelectric, charge transfer, RS232, rs-232
APPLICATION NOTE 651
ESD Protection for I/O Ports
Mar 13, 2000
Abstract: This application note describes how ESD threatens electronic systems, type of damage
inflicted, how ESD is generated, test methods and waveforms used, human body and machine models
for testing, IEC compliance levels, contact and air discharge. Protection methods are described and
Maxim's approach to ESD protection is detailed. Guidelines are given for selecting ICs with high
resistance to ESD. RS-232 I/O ports are specifically considered.
Electrostatic discharge (ESD) can threaten an electronic system when someone replaces a cable or
even touches an I/O port. Discharges that accompany these routine events can disable the port by
destroying one or more of its interface ICs (Figure 1). Such failures can also be costly—they raise the
cost of warranty repairs while diminishing the product's perceived quality.
Figure 1. ICs with inadequate ESD protection are subject to catastrophic failure—including ruptured
passivation, electrothermal migration, splattered aluminum, contact spiking, and dielectric failure.
ESD has another way of causing trouble. Manufacturers may soon be barred from selling to the
European community unless their equipment meets minimum levels of ESD performance. These two
factors, coupled with the increasing amount of electrical communication between computers and
computer-related equipment, lend emphasis to the need for engineers to understand ESD.
A proper understanding of ESD requires an awareness not only of the voltage levels involved, but also of
the voltage and current waveforms, IC-protection structures, test methods, and application circuits. These
matters are discussed in the following sections.
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