According to Pete: Phase-Locked Loops

Without phase-locked loops, we’d all still be living in caves, just getting by with stone knives and bearskins.

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I’m not usually one to go in for sensationalized topics. Clickbait irritates me. But believe me when I say I’m not overstating the importance of phase-locked loops. They live at the heart of every computer system. Phase-locked loops are what make spread-spectrum RF like WiFi and Bluetooth possible.

Really into IoT? You’ve got phase-locked loops to thank. And you know what? Phase-locked loops are tired of being ignored by people who don’t know what they’re all about and how important they are! So if I were you, I’d do the socially responsible thing and watch this video.

Then probably tweet something out about PLLs, saying you’re sorry and telling them how much you love them. And if you do it right, maybe, just maybe, your junk won’t crash today.

Comments 6 comments

  • Valen / about 6 years ago / 1

    Next time, if you can arrange it, please avoid light reflection in the middle of the whiteboard. Good thing you guys used multiple camera angles.

  • JN_Austin / about 6 years ago / 1

    Pete, good attempt. Coming from an analog IC designer who does PLL's you had an uphill battle on your hands. You covered the majority of integrated clocking type PLL's with your description but as others have noted this is just scratching the surface. A clock data recovery type implementation would likely make most of the viewers heads spin but it would be good to see it rolled out.

    .ps The Gardner book is a good one and I can second it as a great resource.

  • Member #543175 / about 6 years ago / 1


    A great video, however I have one major gripe.

    When you start off by saying the topic of PLL is really huge - yes it is, however there are so many engineers who are only aware about the existence of digital/binary PLL's and they think that this is the total extent of the theory and application. What you have concentrated on explaining is a binary PLL which is a very special case of PLLs. You have to understand that when you start looking at Analog or Digital/numeric PLLs there is a whole load more theory and application that you come across.

    I can recommend a great text by Floyd Gardner called "Phaselock Techniques" that actually provides a broad overview of the complete subject of PLL.

    • Thanks for the reference! Your gripe is legit, logged, and not unexpected. As I said in one of the YouTube comments, you can only get so far up Everest in 23 minutes.

  • Member #134773 / about 6 years ago / 1

    Another great video, Pete! I do have one "nit to pick", though: although PLLs are often used to generate a higher frequency than the reference, they can be used to generate a frequency lower than the reference. This can be useful, for instance, when you need some "oddball" frequency, or even more useful if you need to program this output frequency. One place many folks have this in their lives is a digitally programmable AM radio. (The PLL can generate the frequency for the Local Oscillator for your superheterodyne radio, using, say, a 10 megahertz crystal to generate the 1.075 MHz signal to heterodyne with the 620 kHz signal to feed to the [standard] 455 kHz IF strip.)

    • Thanks for that, '773! Although, if I were going to nitpick, I would have gone for the description of how the phase frequency detector pulses and timing worked out. I could have done that better.

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