FAQ Can I perform hot swap on systems using GMSL parts with Phantom Power (aka Power over Coax) where one coax cable is used for data and power

Yes, you can implement a hot swap system with these parts. We have customers with such implementations in production.

There are 3 considerations:

1. Voltages spikes.  PoC systems use inductors in the filter that seperates power from data.  On hot unplug, these inductors can produce high voltage spikes if a discharge path is not provided.  Normally resistors across any inductors can be used to limit the voltage.

2. Current spikes.  When a device in hot plugged, capacitors in the power supply chain need to be charged, some components also have a non-linear I-V curve which can produce spikes.  These current spikes will cause the power rail driving PoC to drop and if anything else is connected to it (or derives power from through a regulator), such a drop may be low enough to cause malfunction.  There are several ways to deal with this: large capacitors on the rail that supplies PoC (normally not practical), using switching regulators with soft start for PoC power, and using an inductor to limit current flow.  Another option is a "high side switch" such as Maxim's MAX16946, which allows control of how the PoC voltage ramps.

3. Re-initializing the device which is hot plugged.  Most plug in devices need to be reprogrammed, so the software responsible for that needs to know when to do it, or needs to know when the device is hot unplugged/plugged.  This can be achieved by adding hardware, or periodically checking registers in the hot swap device.  For instance: if a register is correctly set, the device is plugged in and initialized; if the register cannot be read, the device is unplugged; and if the register reads the power on value, the device has been hot plugged and needs to be initialized.