Understanding the need for ESD suppression in consumer electronics
Tim Micun, Business Development Manager, TVS Diode Arrays
Semiconductor Business Unit, Littelfuse, Inc.
Personal electronics are subjected to unseen destructive forces that are capable of rendering them useless. Whenever two dissimilar materials come into contact with one another, there is always the possibility that the potential imbalance of electrical charges between those two materials will result in an electrostatic discharge (ESD). More commonly known as a “static shock”, these electrical transients can wreak havoc on handheld and wearable consumer electronics. Each time one of these devices is handled by human hands, the potential for an ESD exists. Add to that the numerous cables that can be plugged into various ports on these devices and the risk for damaging the device with a static discharge grows considerably. Even if the shock is not felt, the damage that can be caused by a single ESD event can be catastrophic for unprotected or insufficiently protected components and circuits.
Figure 1: The circuits highlighted in green may experience electrical overstress (over-current, ESD, surge) and may require protection components to ensure reliable performance and/or meet regulatory standards.
ESD is characterized by fast rise times and high peak voltages and currents up to 30A (per IEC 61000- 4-2, level 4), which can melt silicon and conductor traces. See Figure 1. However, the damage caused by ESD effects is not always so apparent. ESD can actually cause three types of damage:
· Soft failures: Electrical currents due to ESD can change the state of internal logic, causing a system to latch up or behave unpredictably, or cause corruption of a data stream. Although this effect is temporary, it may slow down communications or require a system reboot in the case of lockup.
· Latent defects: ESD can damage a component or circuit and degrade its function even if the system continues to operate. However, this type of defect often progresses to a premature failure.
· Catastrophic failures: ESD can damage a component to the point where it does not function as intended, or doesn't work at all.
As IC dimensions continue to shrink, the opportunities for electronic circuit damage increase.
Most ICs operate at low voltages and have structures and conductive paths that are unable to withstand the high currents and voltages associated with ESD transients. As higher frequency communication devices are developed to transmit more information in less time, it becomes increasingly challenging to identify solutions that won't compromise stringent signal integrity requirements at the higher data rates. The ESD suppressors used must have low internal capacitance so that data communication signals are not distorted.
Figure 2: Portable devices like smartphones are subject to a wide variety of electrical threats.
IC designers add a limited amount of ESD suppression to their chips to help prevent damage during manufacturing and assembly processes. However, the level of protection that is added may not be sufficient to protect ICs and other semiconductor devices from ESD during actual use. Many electronic products, especially portable ones,