Docks and USB-C hubs

How Do You Read the HDMI and Charging Specs on a USB-C Hub?

Published · By Ergocrew · Specs and guidance as of that date, from the pages under Sources

Summary

Read the HDMI line for the refresh rate as well as the resolution, since "4K" on a hub can mean 4K at 30Hz. Read the charging line for two numbers, the wattage the hub accepts from your charger and the wattage it passes on to the laptop. Neither figure means anything unless the laptop's USB-C port sends video and accepts power, so that port comes first.

Start with the laptop's port

An HDMI socket on a hub is only an output. The picture has to come from the laptop, down the USB-C cable, and hubs typically carry it using DisplayPort Alt Mode. The DisplayPort FAQ says "Products today claiming 'video over USB-C' are typically using DisplayPort Alt Mode," and that a port without it gives "no image on the screen." Lemorele puts the same point in its compatibility notes. Its TC96 is "Not Compatible" with "devices without DisplayPort Alt Mode over USB-C," and its TC38L is not compatible with "USB-C to HDMI output via data-only ports."

The laptop's spec page should say whether a port carries video. Apple's page for the MacBook Air with M2, for example, lists "Native DisplayPort output over USB‑C."

The HDMI line

Both Lemorele hubs above give the same HDMI figure: HDMI 1.4, "up to 4K@30Hz resolution." That means 30 new frames a second at 4K. If your monitor runs at 60Hz today on a direct cable, it gets half as many frames a second through either hub at full 4K. The number to look for is written as 4K@60Hz or 4K 60Hz, and if the spec page gives only "4K," it hasn't answered the question.

The laptop has a limit of its own here too. Apple lists the M2 MacBook Air at "One external display with up to 6K resolution at 60Hz," so on that laptop the hub, not the Mac, is what sets 30Hz.

The charging line

USB Power Delivery lets each device ask for what it needs. USB-IF describes it as "allowing each device to take only the power it requires." A hub sits in the middle of that. Power comes in from your charger, the hub and the devices plugged into it take a share, and the rest goes to the laptop.

Lemorele's TC96 page gives both ends of that chain: its PD port "supports 100W input and delivers ~85W to charge laptops, tablets, and phones during full-load operations." That's roughly 15W kept back. The TC38L page says it "Delivers up to 100W power through the PD port" and gives no figure for what reaches the laptop. Hub pages vary in this way, and the second number is the one to compare with the adapter that came with your laptop.

Power for the devices plugged into the hub is a separate budget, which our guide to powered USB hubs covers. The limit for USB-C charging itself sits well above both hubs. USB-IF's Power Delivery 3.1 revision raised it to 240W, and before that "USB PD was limited to 100W." Both Lemorele hubs, with their 100W inputs, sit at that older limit.

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Related guides

Sources

  1. DisplayPort (VESA), FAQ
  2. Lemorele, TC96 13-in-1 USB-C Hub
  3. Lemorele, TC38L USB-C 8-in-1 Hub
  4. Apple, MacBook Air (M2, 2022) Tech Specs
  5. USB-IF, USB Charger (USB Power Delivery)

We have not tested these products. Specs and guidance are as published on these pages on the date above and can change; the manufacturer's page for your model has the current details.

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