ISO1212: ISO1212_Current Sink and Source schematic Review

Hi Chitharanjan,

Thanks for reaching out. Here is my review of the schematic:

-I see that you have placed the CDSOD323-T36SC TVS diode on the right side of the RTHR resistor in your schematic, such that the component is connected to both of the IN pins between the J23 connector and RTHR resistor. While this will work, a better alternative is to connect the TVS diode on the left side of the RTHR resistor, such that the component is located between the RTHR resistor and CIN capacitor. In this new configuration, the peak surge current requirement and working voltage requirement for the TVS diode will be reduced. For more information about this, you can refer to the below paragraph from Section 9.2.1.2.5 of the ISO1212 datasheet.

-The maximum clamping voltage of CDSOD323-T36SC TVS diode is 75 V, which is above the absolute maximum voltage rating of the ISO1212 IN pins. To prevent the ISO1212 from being damaged in the event of the TVS diode clamping voltage reaching 75 V, I recommend that you look into selecting a different TVS diode that has a maximum clamping voltage under 60 V. As mentioned by the above paragraph from the datasheet, this requirement should be easier to meet if you move the TVS diode such that it is located on the left side of the RTHR resistor, between the RTHR resistor and CIN capacitor.

Excluding the TVS diode, all other connections in the schematic look good. For the TVS diode, please consider selecting a different TVS diode that has a lower maximum clamping voltage. To see if we can provide a recommendation for a TI TVS diode that is similar to what is currently being used but with a lower maximum clamping voltage, I have notified the protection devices team.

Additionally, please also consider following the recommendation above for connecting the TVS diode between the RTHR resistor and CIN capacitor components.

Regards,

Kenneth