High-speed automotive electronics needs high-performance ESD protection

TVS Diodes

With low clamping voltages and sub-nanosecond response times, TVS diodes are ideal for safeguarding data ports from fast rise-time transient threats (ESD). To minimize the stress voltage to the transceiver IC, a protection device must reduce (clamp) the incoming ESD spike to a safe voltage threshold for the protected IC. During the ESD event, the TVS junction avalanches to provide a shunt path for the transient current while clamping the transient voltage. The clamping voltage is the maximum voltage differential across the TVS device during the transient (ESD) event. This voltage should be well below the destructive threshold of the transceiver IC.

 

While safeguarding the interface transceiver is the most critical part of the protection design, it satisfies only half of the design criteria. Additionally, the protection component must not adversely impact the signal quality. Thus, an effective protection solution should present sufficiently low leakage current and capacitance such that the TVS component is “transparent” to the transmission line during normal data transmission. To achieve this, the capacitance of the TVS should be low enough for the bandwidth of the signal port it is protecting. As an example, for USB 2.0 the TVS junction should generally present less than 3pF. For a higher speed interface, like HDMI, the capacitance should be much lower – less than 0.5pF.