I am designing a PCB with JST EH connectors, which are connected to a multi pin socket exposed to the user. The multi pin socket provides +24V, CAN H, CAN L and GND. I have experienced that the PCB does not like to "hot swap" the connector exposed to the user, and sometimes fail/dies.

It is no problem as long as I disconnect power to the PCB before connecting/disconnecting the connector.

Would like some input/guidance on the PCB design to be able to "hot swap" these connectors. The connectors and socket pins are all equal in length, so GND will not be connected first.

EDIT: The connector brand is CNLinko. Example product: LP-12-5 pin. All pins are equal in length, so GND is not connected first unfortunately. Is there any way to protect the circuit properly when using such a connector?

24VDC input schematic: enter image description here

  • \$\begingroup\$ well, pick different connectors, I guess, would be the design guidance one would expected to get. I bet you've ruled that out due to external factors – but we don't know these, so all our recommendations are likely to just run afoul of them. Please tell us what makes you stick to these connectors if you want hot-plugging! They really seem to be an odd choice to me. \$\endgroup\$ Commented Dec 8, 2023 at 11:22
  • \$\begingroup\$ In what way does the board "fail/die"? My guess is that that is important information. Dead component part numbers / failure mechanism / partial schematic - anything - ? \$\endgroup\$
    – AnalogKid
    Commented Dec 8, 2023 at 13:56
  • \$\begingroup\$ Do you have the typical low-capacitance TVS array protection on the CAN bus lines? \$\endgroup\$ Commented Dec 8, 2023 at 14:12
  • \$\begingroup\$ @SpehroPefhany no but I just read up on that, so will add them for next revision. \$\endgroup\$
    – eidetech
    Commented Dec 8, 2023 at 14:17
  • \$\begingroup\$ @winny I think you mean first-make/last-break; MBB is something else. \$\endgroup\$
    – Hearth
    Commented Dec 8, 2023 at 14:51

1 Answer 1


Is there any way to protect the circuit properly when using such a connector?

The easiest way is for ground to connect first with a connector.


If this isn't a good way you can add a pmos fet to 'block' the voltage to your load safely on connects or disconnects.

Using a high side switch is the only good way I know of to limit startup current and keep current from flowing into the unit. You can use a circuit below or 'roll your own' without a hotswap controller (ie by using just a pull down resistor.)

enter image description here https://www.nexperia.com/applications/industrial-and-power/hot-swap-comms-infrastructure.html


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