ESD

9System-Level EOS Issues for Analog Design

9.1 EOS Protection Devices

Electrical overstress (EOS) protection devices are supported by a large variety of analog technologies [1–24]. Although material and operation may differ between the EOS protection devices, their electrical characteristics can be classified into a few fundamental groups. Figure 9.1 shows the classification of EOS devices.

Figure 9.1 EOS protection device classifications.

EOS protection networks can be identified as a voltage suppression device or as a current-limiting device. The voltage suppression device limits the voltage observed on the signal pins or power rails of a component, preventing electrical overvoltage (EOV). The current-limiting device prevents a high current from reaching sensitive nodes, avoiding electrical overcurrent (EOC).

9.1.1 EOS Protection Device: Voltage Suppression Devices

Voltage suppression devices can also be subdivided into two major classifications [1, 19]. Figure 9.2 illustrates the examples of voltage suppression categories. Voltage suppression devices can be segmented into devices that remain with a positive differential resistance and those that undergo a negative resistance region. For positive differential resistance, these devices can be referred to as “voltage clamp” devices where dI/dV remains positive for all states; for the second group, there exists a region where ...