Placement and values for ferrite bead/capacitor ESD protection / transient suppression filter

by wdbwbd1   Last Updated July 11, 2019 23:25 PM

I've been researching but found it difficult to find a clear answer on this. I need to add ESD protection to my circuit, in this Texas Instruments video it talks about combining a TVS diode with a FBC (ferrite bead/capacitor) filter to maximize ESD protection, which to me seems like the best approach. I am wondering about placement and values for the filter. I will be powering a 3.3V ADC and MCU from a 5V AC adapter as shown in the schematic. Would the best placement of the FBC filter be right at the start of the circuit at the output of the AC adapter? I saw mention of using them at other places in the circuit and I think I saw using multiple FBC ESD filters mentioned. To me it seems like just one at the start of the circuit should work well but that's just my unknowing guess.

I am also looking for general values for the bead and capacitor. Most beads I looked at have a resistance of about 20-200 ohms at 100MHz. What size bead and capacitor would be ideal for ESD transient suppression? Should the capacitor be smaller value, or larger which could also double as a bulk supply decoupler for the circuit? Does the capacitor type matter? I've seen many mentions of the filter used but values have not been described. Thanks very much for any help.

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