ESD device classification and Murata A-TVS characteristics

1. Classification of ESD devices

ESD (Electro-Static discharge) devices are also known as electrostatic protection devices. Common ESD protection devices mainly include varistor, TVS diode of silicon material and A-TVS of Murata ceramic material.

The varistor is a voltage-limiting protection device. When subjected to ESD, the varistor can clamp the voltage to a relatively fixed voltage value, thereby realizing the protection of the subsequent circuit. However, its ESD performance will deteriorate with increasing use times, simple structure, cheap materials and extremely low cost.

The TVS diode of silicon material uses the principle of PN junction reverse breakdown avalanche. When experiencing an ESD event, it instantly transfers energy out and has no effect on the device itself. But affected by the process, the cost is higher. Especially for TVS used on high-speed data lines, the lower the parasitic capacitance required, the higher the cost.

Murata ceramic-based A-TVS uses the principle of inter-electrode discharge and can withstand more than 10,000 ESD tests. The integrated capacitance is very low and can achieve 0.05Pf, so it is particularly suitable for high-speed data lines, and the cost is also low. As long as 0.001 ~ 0.002USD, ESD protection can be achieved.

2. Murata A-TVS features and applications

According to the connection shown above, Murata's A-TVS is used with capacitors. Compared with traditional silicon TVS devices, it has the following characteristics:

• No harmonic noise. As shown in the figure below, silicon TVS is prone to generate harmonic noise, which interferes with the signals received and transmitted by the RF antenna, while A-TVS has no harmonic noise.

• Low insertion loss Murata's unique ceramic ESD product, tested at 2.4GHZ, insertion loss is only -0.004dB, equivalent capacitance value is as low as 0.035pf, in line with IEC61000-4-2 static 15kV test, and has a good Repeatability. Compared with the traditional silicon material TVS, the equivalent capacitance value is more than 0.1pf, Murata's ceramic A-TVS has great advantages. Therefore, such products are particularly suitable for high-frequency signal lines, such as main antenna, GPS antenna, WIFI antenna, NFC antenna, etc.

• The peak voltage under static test is low. As shown in the figure below, according to the test conditions of IEC61000-4-2, Murata's A-TVS can achieve a lower clamping voltage, thereby protecting the circuit more safely.