Designing Electronic Systems For Esd Immunity

FEATURE www.conformity.com Designing Electronic Systems For ESD Immunity Here’s A Comprehensive Checklist To Ensure That Your System Is Properly Protected his article describes over 140 different ways to make your electronic equipment and electronic products immune to electrostatic discharge (ESD). Many of these techniques can also improve your system’s electromagnetic compatibility (EMC), electromagnetic interference (EMI), and overall robustness. T An ESD arc is an intense noise source with significant energy from 1MHz to 500MHz. This energy penetrates your system by every means possible, coupling into cables and printed circuit boards (PCBs), and may cause system upsets, lock-ups or unwanted resets, as well as lost data and risk of permanent damage. The key to effective immunity against ESD is to begin early in development, following conservative design practices and providing “wiggle room” in areas where you may need to tweak your design. ESD testing throughout development can also help you to find and fix weak spots as you go. Specifically, we defend against ESD by reducing the coupling into your system, and by making the system immune to transients through use of any or all of the following methods: ● Plastic enclosures, air space and insulation. 18 CONFORMITY ®: FEBRUARY 2003 ● Metal enclosures and shielding. ● Grounding and bonding. ● Power distribution, bypassing and decoupling. ● PCB design and mounting. ● Cable design and routing. ● Filters and transient suppressors. ● Robust components. ● Robust circuit design. ● Watchdog timers. ● Software. ● ESD testing to find and fix weak spots. Plastic Enclosures, Air Space And Insulation Plastic enclosures, air space, and insulation prevent ESD arcs to a system (direct ESD): 1. For >=20kV breakdown voltage, keep >=20mm air-path length between electronics and: - Any points tha