Sometimes the naming of parts in electronics can lead to confusion about what they are good for, with the topic of zener diodes in the context of fast currents such as that of electrostatic discharge (ESD) being a good example. In a recent video by [BTT Lab] this particular question about the zener’s suitability for suppressing ESD is addressed, compared to transient-voltage-suppression (TVS) diodes.
The main argument against the use of zener diodes for ESD and similar surge suppression is that they react too slowly, which of course is said to take time to cause real damage. This is where a special form of avalanche effect based diodes called TVS diodes are recommended because their response time is in the picoseconds rather than nanoseconds or slower than for zener diodes.
While this is technically correct, as indicated in the video, a zener diode also uses the avalanche effect, with the diode starting to conduct in the reverse direction with the zener effect before transitioning to the much faster avalanche effect. The transition point is determined by how heavily doped the pn-junction is, effectively making all Zener diodes avalanche diodes as well.
TVS diodes are therefore basically Zener diodes, which are optimized for a very early transition to the avalanche effect. They are also generally larger than typical Zener diodes because they generate a lot of internal thermal energy while in reverse conduction mode that must be contained and dissipated without causing permanent damage.
So the short version is that diodes marked as ‘TVS’ are the best choice for surge protection, while those marked as ‘Zener’ are best used for bucking voltages, reference voltages and all the other typical zener diode stuff.