ESD
What is ESD?
Definition
Electrostatic Discharge (ESD) is the release of stored static electricity. Most commonly, it refers to the sudden, potentially damaging discharge of many thousands of volts that occurs when an electronic device is touched by a charged body.
When does ESD occur?
ESD results from one of two conditions:
- Contact discharge: Direct contact transfer between two objects at different potentials.
- Air discharge: A high electrostatic field between two objects when they are in close proximity.
How does ESD damage electronics?
The most common manifestation of ESD damage is a catastrophic failure of the IC. However, exposure to ESD can also cause increased leakage, or degrade other parameters. The effects of ESD damage can be cumulative, so repeated mishandling of a device can eventually cause a failure.
ESD Warning Symbols
ESD-sensitive devices are shipped in protective packaging and are marked with special handling instructions. Below are symbols used to indicate ESD-sensitive devices.
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ESD Models
The three most prominent waveforms to evaluate ESD susceptibility for semiconductors or discrete devices are The Human Body Model (HBM), the Machine Model (MM), and the Charged Device Model (CDM). Each of these represents a fundamentally different ESD event, so correlation between test results is minimal.
ESD Protection
There is no way to undo ESD damage or to compensate for its effects, so prevention is key. Protecting ICs from ESD requires the participation of both the IC manufacturer and the customer. Devices themselves can be designed to minimize ESD, but users of those ICs must also have the necessary knowledge of, and training in, ESD handling procedures. Precautions should be taken when handling ICs, such as wearing a conductive wrist strap and having static-dissipative workbenches and mats.
ESD protection is built into most ICs. Devices can be added to input and output pins on an IC to protect the internal circuitry from the damaging effects of ESD. ADI makes specialized ESD-protection and other fault-protected devices, including ESD protection diodes, analog switches and multiplexers, switch debouncer/protectors, overvoltage protection (OVP) controllers, signal-line protectors, lithium-ion (Li+) battery protectors, and current-limit and USB power switches.