To begin the design process, consider the following parameters:

• Ensure the voltage range on the protected line does not exceed the reverse standoff voltage of the TVS diodes (V_RWM).
• Ensure the operating frequency is supported by the I/O capacitance (C_IO) of the TVS diode.
• Ensure the IEC 61000-4-2 protection requirement is covered by the IEC performance of the TVS diode.

For this application, the audio signal voltage range is –8 V to 8 V. The V_RWM for the TVS is –9.5 V to 9.5 V; therefore, the bidirectional TVS will not break down during normal operation, and normal operation of the audio signal will not be affected due to the signal voltage range. In this application, a bidirectional TVS like TPD1E10B09 is required.

Next, consider the frequency content of this audio signal. In this application with the class AB amplifier, the frequency content is from 20 Hz to 20 kHz; filter the TVS I/O capacitance so that it does not distort this signal. With TPD1E10B09 typical capacitance of 10 pF, which leads to a typical cutoff frequency of just under 500 MHz, this diode has sufficient bandwidth to pass the audio signal without distorting it.

Finally, the human interface in this application requires protection for ±15-kV Contact and ±15-kV Air-Gap ESD, which is above the standard Level 4 IEC 61000-4-2 system-level ESD protection. A standard TVS cannot survive this level of IEC ESD stress. However, TPD1E10B09 can survive at least ±20-kV Contact and ±20-kV Air-Gap ESD. Therefore, the device can provide sufficient ESD protection for the interface, even though the requirements are stringent. For any TVS diode to provide its full range of ESD protection capabilities, as well as to minimize the noise and EMI disturbances the board will see during ESD events, it is crucial that a system designer uses proper board layout of their TVS ESD protection diodes. For instructions on properly laying out TPD1E10B09, see Layout.