Contact discharge or air discharge?

AN3353

2/9

Doc ID 018527 Rev 1

1

Contact discharge or air discharge?

According to the standard, contact discharge is the preferred test method. Air discharge

shall be used when contact discharge cannot be applied. Contact discharge is more

dedicated to conductive surfaces and air discharge to insulating surfaces. In case of air

discharge, the current level and rise time are less reproducible and more related to

environmental conditions (humidity, speed of the tip approach etc.).

However, STMicroelectronics protection devices are always specified according to the two

test methods, and the specified levels are most of the time the maximum standard levels.

That is to say 8 kV for contact discharge and 15 kV for air discharge (level 4 of the standard).

Note:

The clamping voltage waveforms of our protection devices given in the datasheets are

measured at 8kV in contact discharge. This test condition gives the worst case clamping

voltage response because the rate of rise of the current gets its highest value (around

45 A/ns). (See Section 5: Clamping voltage measurement.)