6 Absolute maximum ratings of TVS diodes (ESD protection diodes)

Absolute maximum ratings

Definition
For ESD protection diodes, the maximum allowable current, voltage, power dissipation, and other characteristics are specified as maximum ratings. In circuit design, understanding maximum ratings is crucial in order to obtain the best performance from ESD protection diodes and maintain the device reliability throughout their target operating life. In order to guarantee the lifespan and reliability of ESD protection diodes, maximum ratings must not be exceeded. For ESD protection diodes, maximum ratings are defined in accordance with the absolute maximum rating system. The absolute maximum ratings are the highest values that must not be exceeded even instantaneously under any conditions. If a stress exceeding the specified rating is applied, a device might be permanently degraded. None of the absolute maximum ratings may be exceeded. Therefore, care should be exercised as to supply voltage bounces, variations in the characteristics of electronic devices, possible exposure to stress higher than maximum ratings during circuit adjustment, changes in ambient temperature, input signal fluctuations, and so on. The major ratings that should be considered include the ESD tolerance, peak pulse power, junction temperature, and storage temperature of ESD protection diodes. These parameters are interrelated and cannot be considered separately. They also depend on external circuit conditions. Although the absolute maximum ratings are generally specified at an ambient temperature (T_a) of 25°C, some parameters are specified at different temperatures.

Electrostatic discharge voltage (IEC 61000-4-2) (contact), V_ESD
This is the ESD tolerance to a contact discharge, i.e., a discharge through direct contact with equipment under protection. The ESD tolerance is measured according to the method and ESD waveform specified in the IEC 61000-4-2 standard from the International Electrotechnical Commission (IEC). The specified VESD value is the peak value of the test waveform.

Electrostatic discharge voltage (IEC 61000-4-2) (air), V_ESD
This is the ESD tolerance to an air discharge, i.e., a discharge that occurs between equipment under test (EUT) and a discharge gun through an air layer. The test method and the ESD waveform are specified in IEC 61000-4-2.

Peak pulse power (t_p = 8/20 μs), P_PK
P_PK is the maximum surge power that can be shunted before an ESD protection diode itself is damaged. The peak pulse power is measured using an 8/20 μs pulse waveform shown in Figure 6.1. (8/20 μs means that it takes 8 μs for the waveform to rise to 100% and 20 μs to fall from 100% to 50%.)

Peak pulse current (t_p = 8/20 μs), I_PP
I_PP is the peak pulse current that can be shunted before an ESD protection diode itself is damaged.
The peak pulse current is measured using a test waveform shown in Figure 6.1 compliant with IEC 61000-4-5.

Junction temperature, T_j
T_j is the maximum junction temperature at which an ESD protection diode can operate without degradation or self-damage.

Storage temperature, T_stg
T_stg is the ambient temperature range in which an ESD protection diode can be stored and transported without voltage application.