HDMI Cable Power – HDMI 2.1a Amendment 1
Currently HDMI cables only support the transport of 5VDC@50mA for handling CEC/EDID. Their primary function is to carry digital data and signaling, not DC power. For those that need long HDMI cable runs, especially for 18 and now 48Gbps, this meant one of two approaches:
- Using active cables whose electronics draw power DIRECTLY from the DISPLAYS HDMI connector or
- Adding a power inserter and external WalWart power supply to power the cable electronics and/or some form of HDMI extender.
HDMI sockets have the ability to provide at least 50mA at 5volts. In most cases that is sufficient to power active optical or copper HDMI cables that handle up to 48Gbps.
Amendment 1 to the specification for HDMI 2.1a has now been announced that adds a new feature called HDMI Cable Power. It purpose is to enable users to deploy high speed HDMI cables that are much longer than are currently supported, without the need for a separate power connector.
Current passive cables are limited in their length if they are to support HDMI 2.1’s fixed rate link signaling system, which delivers ultra-fast, high bandwidth 48Gbps signals over passive cables up to 16 feet or so. This length restriction was overcome using quite expensive active copper or active optical HDMI cabling.
This new amendment allows HDMI Power Cables to pass up to 300mA directly from the sources HDMI connector, potentially simplifying cable runs in home cinema systems. The standard also allows for the HDMI chips to “signal to the cable” what the HDMI sockets maximum current capacity is.
In order for this feature to work both the cable and source devices will need to support Cable Power and you’ll also need to make sure your cable is plugged in the right way, as the feature only works in one direction. (Just like the current active HDMI cables.)
Even if your current hardware does not support cable power, Cable Power compatible cables will be offered with USB Micro-B or Type-C connectors for source devices that do not support the standard, thereby allowing for easier connectivity?
The bad news is that this feature may require new HDMI chips in source devices for it to work. This means that your current gear may not support the function through a firmware update.
It looks to me like these new longer high speed HDMI 2.1a Power Cables are just the current 18/48Gbps optical/copper active HDMI cables that will carry a little more DC power, plus an additional source DC power connector.
FSR Optical 18/48 Gbps active HDMI cable. Current draw 50mA (0.25watts)
To be honest I do not really see the need or advantage of this amendment 1. The long (up to 50 feet) active copper/optical 10.2Gbps and 18Gbps HDMI cables that I have tested and now use, work just fine using power DIRECTLY from the DESTINATIONS (displays) HDMI connector. These optical cables can be over 300 feet long at 18Gbps and 100 feet long at 48Gbps. Maybe this is a solution in search of a real problem?
There is no need for this cable for short runs of up to 16+feet, as currently certified 8K passive cables work just fine. So these new Power Cables are ONLY for longer runs, what is wrong with the current 18/48Gbps active cables? Maybe volume production will bring down the cost of these new active versions. I also wonder if the feature is to allow other HDMI destination devices to draw power from the HDMI Power Cable rather than you having to plug it into an AC power source. If so 5VDC@300mA (1.5watts) is not much power for any additional device.
So for now we wait to see the final vendors high speed HDMI 2.1a Power Cable and associated HDMI chip/socket specifications.
For more information on HDMI Cable Power see HDMI.org
For more information on HDMI 2.1a see HDMI.org.
Want a quick recap on HDMI 2.1 features read this post.
See my review of the FSR active Optical HDMI cable here
See my review of the Monoprice and C2G active optical cables here.
