If you’ve seen a lightning bolt or been unpleasantly shocked by a doorknob, you’ve been exposed to the phenomenon known as electrostatic discharge (ESD). ESD is the sudden flow of electricity between two charged objects that come into close proximity. Objects that are in contact sometimes cause a discharge of electricity to go directly from one object to the other. Other times, the voltage potential between the objects can be so great that the dielectric medium (usually air) between them breaks down – contact isn’t even necessary for the electricity to flow (Figure 1).
Figure 1: Electrons transferring between two charged objects result in ESD
These shocks happen all the time, but humans can’t feel most of them because the shock voltage is too low to be noticeable. Most people actually do not start feeling the shock until the discharge exceeds 2,000-3,000V! While ESD in the 1-10kV range is typically harmless to humans, it can cause catastrophic electrical overstress failures for semiconductors and integrated circuits (ICs).
ESD suppressors or diodes placed in parallel between the source of ESD (typically an interface connector to the outside world) and the component (Figure 2) can protect system circuitry from electrical overstress failures.
Figure 2: An ESD strike will damage an IC without ESD protection (left); ESD protection will shunt current to protect the downstream IC (right)
Without ESD protection, all of the current from an ESD strike would flow directly into the system circuitry and destroy components. But if there is an ESD protection diode present, a high-voltage ESD strike will cause the diode to breakdown and provide a low-impedance path to redirect the current to ground, thus protecting the circuitry downstream.
Many circuit components include device-level ESD protection, which has led some to question the need for external ESD protection components. However, device-level ESD protection is nowhere near robust enough to survive ESD strikes discharged onto real-world end equipment. And as chip sets decrease in size due to process innovations, their susceptibility to ESD damages actually increases, making discrete ESD protection a necessity for every circuit designer.
In the next installments of this five-part series, I will go over the different features and requirements for selecting the proper ESD protection diode. In the meantime, get more information on TI’s comprehensive portfolio of protection solutions for ESD and surge events.
Additional Resources:
- Learn more about TI's ESD products here.