How to design ESD protection for sensitive ICs?

0. Summary

This article answers some Frequently Asked Questions about ESD protection of sensitive ICs.

1. Are there other types of ESD protection without using TVS?

Other type of ESD protection can be: MOV, polymer and PCB spark gap. All of them present very high clamping voltage and reliability issues that are not compatible with ESD protection of sensitive ICs.

2. Is it critical to have the track on the PCB from the ESD source to the ESD protection device rated for the ESD maximum discharge current defined by the ESD level?

The track maximum DC current is not critical due to the ESD event duration (≈100 ns).

3. How do you connect the shield of the connector to the PCB?

We usually connect it to the GND of the system.

4. Where to connect ESD protection ground? 0 V or GND?

ESD protection ground must be connected to the reference GND plane of the protected I/O to limit or avoid any parasitic inductance effect due to multiple ground planes connection.

5. Can you explain why ESD protection is needed with a USB-C connector housed in a plastic case? Because of the shield ground all around the USB contacts (VBUS and signals) it is impossible to touch contacts directly.

ESD cannot be assimilated to simple conduction thought a metal track, it is a charge equilibrium between two systems. As a consequence, air discharge can appear, and non-conductive materials can let the charge flow (e.g. side key buttons on smartphone need to be protected).

6. When protecting an IO power line, the decoupling capacitor also lowers the voltage when a charge is injected, but are there specific requirements for this capacitor?

On power line, capacitors are selected to fit the power requirement. The capacitor rated voltage must be higher than the clamping voltage of the TVS to avoid the degradation (or the destruction) of the capacitor.

7. If I choose for my design the ESDLIN1524BJ close to input current, can I
place it at power inputs also to protect voltage regulators?

Power inputs are usually protected using TVS rather than ESD protection components.
Automotive TVS portfolio is available here .
Industrial TVS portfolio is available here .