The TMUX7308F and TMUX7309F are not intended for standalone electromagnetic compatibility (EMC) protection in industrial applications. There are three common high voltage transient specifications that govern industrial high voltage transient specification: IEC61000-4-2 (ESD), IEC61000-4-4 (EFT), and IEC61000-4-5 (surge immunity). A transient voltage suppressor (TVS), along with some low-value series current limiting resistor, are required to prevent source input voltages from going above the rated ±60 V limits.

When selecting a TVS protection device, it is critical to ensure that the maximum working voltage is greater than both the normal operating range of the input source pins to be protected and any known system common-mode overvoltage that may be present due to incorrect wiring, loss of power, or short circuit. Figure 9-2 shows one example of the proper design window when selecting a TVS device.

Region 1 denotes the normal operation region of TMUX7308F and TMUX7309F where the input source voltages stay below the fault supplies V_DD and V_SS. Region 2 represents the range of possible persistent DC (or long duration AC overvoltage fault) presented on the source input pins. Region 3 represents the margin between any known DC overvoltage level and the absolute maximum rating of the TMUX7308F and TMUX7309F. The selected TVS breakdown voltage must be less than the absolute maximum rating of the TMUX730xF but greater than any known possible persistent DC or long duration AC overvoltage fault to avoid triggering the TVS inadvertently. Region 4 represents the margin that system designers must impose when selecting the TVS protection device to prevent accidental triggering of the ESD cells of the TMUX7308F and TMUX7309F devices.

Figure 9-2 System Operation Regions and Proper Region of Selecting a TVS Protection Device