LG UltraFine 4K PD via USB-C to Windows laptop

pistabaaa · November 16, 2020

Hey guys!

I ran into a setup where I got stuck and couldn't get to either make it work or to find the exact reason why it won't work. So please, help me out if you can! :)

The setup:

LG UltraFine 4K (24MD4KL-B) display with Thunderbolt 3 + USB-C hub in one of the USB-C ports

MacBook Pro (2018) with Thunderbolt 3 connected to the TB3 input with TB3 cable

Xiaomi MiBook Air 13.3" (2016) with USB-C 3.1 gen 1 connected to the TB3 input with either TB3 or USB-C cable, Windows 10

The good:

The display works like a charm with the MacBook Pro, normal USB devices attached through the USB-C hub are recognized and working, MacBook is charged ---> all with a single TB3 cable

The display is getting video/audio signals from the MiBook ---> with TB3 or USB-C 3.1 cable

The bad:

The display is not charging the MiBook, however both supports PD and the MiBook only needs 45W while the display can charge with up to 85W. I tried with TB3 cable and USB-C 3.1 gen 1 cable with PD support and none of them worked.

Yes, the MiBook only has a USB-C 3.1 gen 1 port, but that's where it gets power from the original power brick and it works just fine.

Also the USB-C hub and the connected devices are not showing up on the MiBook with Windows 10.

The weird:

Previously I had a Philips 258B6QUEB display which has USB-C 3.1 gen 1 input and also support PD (up to 60W) and it was working with both the MiBook and the MacBook without an issue (charging as well) and without any additional drivers.

The question:

So what am I missing? Why is the LG UltraFine not charging my MiBook? As far as I know, TB3 is backward compatible with older USB-C standards and power delivery should work.

And although it's not the most important thing to get the USB-C hub working with the MiBook it'd be a nice to have.

Any help would be appreciated!

Have a good one,

Pistabaaa^