Turn off power to Thunderbolt device while leaving data connection

As per the title, is it possible to do this?

I have two devices using Thunderbolt 2 ports on a macbook pro. One, an audio interface, makes the area around the port excessively hot to touch and can cause the fans on the laptop to kick in at a certain point.

I was unsure why only one device caused this when the other (an external display) didn't and realised that the audio interface was also drawing power. The thing is, it doesn't need to. It can be powered externally and I do this. But it automatically chooses a preference for thunderbolt power and switches to this when enough is available.

I'd love to know a way to provide no power over that Thunderbolt port so that it relies on the external power supply and stops generating so much heat (the fans kicking in when I'm recording audio - it being an audio device that's causing this - is far from ideal).

Solution 1:

Per the thunderbolt specification, it includes power so if you could turn it off, it wouldn't be thunderbolt. I suppose a device on the receiving end could have a switch or power control to disable draw, but I have not seen any hardware that assumes anything but you get power at the same time / before any data connection comes alive on thunderbolt.

It's an interesting thought experiment to think if we had this to help troubleshoot, but not something I see as practical. You'd need an oscilloscope and trace to determine what's happening in your setup if you can't measure voltage lines with a multimeter.

Some USB devices have external power and won't draw as do some rack mountable thunderbolt audio devices but they never draw power from TB so you might need to look in that direction if you can't isolate it by swapping in and out parts entirely.