Even ESD protection diodes fail to protect the DUP. What is the cause of its destruction?

In the event of an ESD strike, ESD protection diodes shunt much of the ESD energy to ground to protect the device under protection (DUP). However, the ESD protection diodes must be used properly so that the DUP is not degraded or destroyed by ESD.

As regards ESD protection diodes not working properly, there are two major causes.

  • The selected ESD protection diodes are not suitable for protecting the DUP.
    The higher the clamp voltage (VC) of ESD protection diodes, the greater the ESD energy applied to the DUP. So, you should not select ESD protection diodes with clamp voltage higher than necessary. If there are two ESD protection diodes with equal clamp voltage, selecting the one with lower dynamic resistance also helps improve the protection performance.
    (For details, see the FAQ entry “How to select TVS diodes (ESD protection diodes).”)
    How to select TVS diodes (ESD protection diodes)
Figure 1 Example of ESD protection diode insertion
Figure 1 Example of ESD protection diode insertion
Figure 2 ESD protection diodes with different clamp voltages
Figure 2 ESD protection diodes with different clamp voltages
  • The layout of ESD protection diodes is not good.
    Even the optimal ESD protection diodes do not provide sufficient protection performance unless  they are laid out properly. Since an ESD pulse is very short, it is greatly affected by trace inductance. ESD protection diodes are inserted between a possible ESD entry point such as a connector and the DUP.  ESD protection diodes should be placed as close as possible to the ESD entry points. In addition to the signal line to be protected, the ground trace should be short and wide and should not run through via holes.
    (For details, see the FAQ entry “Board design considerations for TVS diodes (ESD protection diodes).”)
    Board design considerations for TVS diodes (ESD protection diodes)
Figure 3 Examples of layout of ESD protection diodes
Figure 3 Examples of layout of ESD protection diodes

Related Links

For TVS diode (ESD protection diode) products, please refer to the following links.

TVS Diodes (ESD Protection Diodes)
Products
Basics of TVS Diodes (ESD protection diodes)
e-Learning

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