Circuit Protection of Audio - Microphone

Design Notes:

Protection Application:
For the microphone lines, the typical signal has maximum value of 5.5 Vp-p, and has a maximum frequency less than 10kHz. At this frequency, the capacitance of the suppressor does not need to be taken into account. The electrical threat is ESD.
Solution Description:
As shown at the left, discrete multilayer varistors can be used for layout flexibility. Due to the analog nature of the audio signals, uni-polar TVS diode arrays are recommended only if the negative part of this signal is -0.5V or less since they may clip the negative part of the audio signal if the magnitude is larger.
Companion Solutions:
Other solutions within the Littelfuse MLV portfolio exist in addition to these recommendations. For example, if the manufacturing process cannot handle 0402-size components, devices with the same characteristics can be found in 0603-size.
Regulatory Issues:
The IEC 61000-4-2 will be the most appropriate standard that applies for this port. It supplies a test method for verifying that the end product is not susceptible to ESD events.
Unique Features:
Does not apply.
Application Warnings:
Does not apply.