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I've used this ESD circuit on four boards for hobby projects. I have had no issues on two boards. On two others, the TVS diode for VBUS conducted when the board was plugged into a USB port, causing an overcurrent condition and destroying the ESD suppressor (the host is grounding the USB shield). The two working boards have probably just not seen a transient on connection.

Is there a better design for this? Should there be a resistor between the suppressor and shield ground? I have not seen this in the reference designs I see published by companies that make TVS diodes and worry this could slow transient response or prevent conduction.

The ESD suppressor in the circuit is a TI ESDS314DBVR, which is four TVS diodes in one package tied to a common ground. Digikey link https://www.digikey.com/product-detail/en/texas-instruments/ESDS314DBVR/296-ESDS314DBVRCT-ND/9745477.

The PTC is a LittleFuse rated for the power requirements of the board.

Schematic

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    \$\begingroup\$ Who designed the circuit and to what surge or ESD requirement (EN61000 for instance) was it designed to? \$\endgroup\$ – Andy aka 2 days ago
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    \$\begingroup\$ I think the part is an ESDS314DBVR. \$\endgroup\$ – rdtsc 2 days ago
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From the datasheet:

enter image description here

Breakdown voltage, IO to GND is the critical parameter. Some parts may conduct at 4.5V, shorting the 5V VBUS to ground and other may not. This is not a suitable part for VBUS ESD protection.

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  • \$\begingroup\$ That's a good find +1 \$\endgroup\$ – Andy aka 2 days ago
  • \$\begingroup\$ Oh, that is a good find. I missed that in the data sheet. Thank you. \$\endgroup\$ – Brian Pepin 2 days ago

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