Analyze ESD static protective elements

Any protection element must appear at the protected input terminal as a high impedance circuit during normal operation. The capacitive load applied by it must be as small as possible, so that it has little impact on the normal input signal. However, at the moment of overvoltage, the same device must become the main energy path to transfer energy from the input of the protected device. In addition, the standing off voltage of the protection device must be higher than the signal voltage allowed by the protected terminal. Similarly, its clamping voltage must be low enough to prevent the protected device from being damaged. This is because during the transient, the voltage on the input terminal will be the clamping voltage of the protected device.

We often see the introduction of ESD electrostatic protectors, ESD electrostatic impedance devices, ESD electrostatic emitters, patch varistors and other products, but in fact, the key reference coefficients of protective devices should be the following three items:

1. Fast response time

2. Low clamping voltage

3. High voltage stray surge withstand capacity

No matter how excellent the products are introduced, when selecting ESD electrostatic protection components, we should still carefully make practical comparison and use IEC61000-4-2 test to verify. The current industry practice is to publish the clamping voltage according to the 8us rise time and 20us duration pulses, while the real ESD pulse should be 1ns rise time and 60ns duration.