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HDMI: No Active Cable Power Supply, No Problem

Power management techniques are incorporated into HDMI designs that allow power to be consumed throughout every portion of the interface.


The before and after sequence of an HDMI Equalizer with power management.(Click here to enlarge image)

When new technology surfaces, it tends to start off on a bumpy road involving debugging, new problems, and the learning curve it takes to implement these new systems into our industry. Yet talented hardware and software firms take what we have and develop better ways to use these new systems as they are introduced.

One major benefit of an HDMI cable over other transmission devices is that it has all the necessary mechanics to carry this ever-so delicate data consisting of timing, shielding, supply voltage and frequency response. As long as the user doesn’t go crazy with the length, and the cable’s performance is high to begin with, the probability of something going wrong is small. In the past, it was common to add external HDMI equalizers as a patch to achieve longer distances and in many cases they worked pretty well.

Then some companies began to incorporate these same devices used for HDMI cable extenders with alternative cables like Category 5 and 6. But here, again, because this was a cable that was never designed to support a transmission line like HDMI, there were side effects that introduced a high risk of problems at the time of installation or even weeks and even months later. Even if it all worked we still had to contend with one or two more boxes that had to be installed, mounted, hidden and powered.

The good news is that there are a few semiconductor companies that have designed and built some newer devices that are so small they can be installed into the HDMI connector itself. In addition, there have been great successes in eliminating the external power supply (wall wart) that has plagued flat panel installations.

We have talked about the importance of the power supply over and over. In fact, just this last month, we found a series of products that were very squirrely in operation due to noisy power supply issues. It is important that every product practices good power management toward the health of the lifeblood HDMI needs to live on.

Just when you think we have exhausted every ounce of creative juices from the technology grapevine, a new set of ideas and hardware becomes available, helping us to inch our way to length independence. There are now semiconductor firms offering chipsets that are micro mini devices with very tiny footprints and offer the same types of equalized gain that our old extenders did. Even better,they are performing the job with no external power supply. So how does that work?

This is all really cool. By testing these devices and examining their operation we have discovered that these devices can supply the necessary gain to go the distance while at the same time staying within the critical HDMI limits for the online power supply. This became pretty evident to us when one of these devices came in for testing.

One of the many factors we check for is supply voltage. In order to do that we must disconnect the bench HDMI power and reconfigure the probes to make the necessary measurement. Except this time something happened that had never happened to us with any active cable product: When we killed the HDMI power, the cable continued to perform. How could that be? Depending on the cable manufacturer’s choice of semiconductor for these active devices, some can actually operate with no power supply, yet can still deliver the necessary gain needed for Deep Color, 3D, and 4Kx2K.

Power management techniques are incorporated into these designs that allow power to be consumed throughout every portion of the interface rather than just the power supply itself. Is that not cool or what? In the months to come we will begin to see even better cable products with longer lengths enter our distribution channels that will expand our capabilities while keeping the blue side up,1 to boot. All Good Juju for sure.

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Article Topics

News · Wire and Cable · HDMI · All topics

About the Author

Jeff Boccaccio, President, DPL Labs
Jeff Boccaccio, president of DPL Labs, can be reached at

3 Comments (displayed in order by date/time)

Posted by Tuck  on  02/08  at  07:46 AM

The subject of an article should NEVER have HDMI and “no problem” in it! LOL

Posted by Andrew Jackson  on  02/08  at  09:24 AM

What no mention of HDBase-T?  Oh hang on a minute DPL labs don’t sell that.  I’ve been to one of Jeff’s seminars where he absolutely, categorically and completely said that it would never be possible to send HDMI any distance reliably over Cat 5.  Of course he’s sure to ensure that no one takes any recordings in these sessions in case someone finds out that Good JuJu is actually VooDoo

Posted by jbrown  on  02/11  at  11:18 AM

Stop trolling Andrew, HDBaseT has nothing to do with this article.

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