Between the resulting thermal management issues and reduced battery life, linear regulation is seldom worth the pain.
I'd argue the exact opposite. The article is targeting "enthusiasts", and a very large portion of enthusiast projects are going to be powered by a 5V USB charger and consume in the order of a few 100mA of power.
LDOs are dirt cheap, widely available, have pretty decent output characteristics, and incredibly easy to use. If you have basically unlimited 5V and want 100mA of 3.3V, why not use one?
On the other hand, buck converters require you to actually do some actual engineering. You can't just haphazardly throw in a single IC and expect it to work flawlessly on your first try. You either have to use an (expensive!) fully-integrated module, or do a decent bit of math and part sourcing yourself. Neither option is exactly attractive to a hobbyist building a fairly simple one-off PCB.
Linear regulation is also very good when you have situations where you want to avoid generating unwanted noise or stray RF.
Cheap buck converters are very noisy and annoying if you are building an audio or radio related project, or have such things nearby.
In my experience, not only noise in the RF sense, but also audible. I put together a little audio amplifier, and the sound of the DC/DC makes it unusable in quiet situations. The 12kHz (coming physically from the converter, amplifier off) really hurts the ears!
That’s magnetostriction, components under switching load (caps, inductors) need to be secured in place with an appropriate glue/putty.
Using a higher switching frequency can also help, plenty to choose from.
Can that also help with the emanations security issue where an adversary might be able to extract usable data from the audio produced by the electronic components?
The usable data would just be "DC-DC converter is on/off". In theory, if the converter uses a variable frequency or duty cycle, you might be able to extract some information about that too. But that's not very interesting.
A DC-DC converter always uses a variable duty cycle to maintain the target output voltage (or for CC, current). Without it, the voltage would vary wildly depending on load.
For something like an audio amplifier, obtaining precise power supply load would in turn give you a curve over amplifier load, which effectively gives you the speaker amplitude. Input caps and filtering will likely remove the high frequency components entirely, but you might be able to construct at least part of the played waveform.
All good points. I would say that it's a fairly outlandish scenario where you are (i) close enough to the device to listen to the caps whining but (ii) can't measure actual voltages within the circuit (which could be a lot more informative) and (iii) can't just listen to the audio output of the device directly.
Acoustic noise is one thing, but it's not at all outlandish to be within range of the EMI emitted from the same power supply which tells the same tale. What is outlandish is thinking anyone bothers listening in. :)
TEMPEST and other side-channel hardening is hard to do if you lack access to anechoic/RF isolated chambers, sensitive scopes/microphones and knowledge.
yes, but the audio usually doesn't travel as far as the rf; you'd almost have to be in a situation where the adversary can't put equipment near you but has managed to subvert a microphone
The noise would correlate with load, but this is the least of your worries.
Unless you have a proper RF testing lab and skilled EMC engineers at your disposal, the only thing you can do is stuff everything into a properly designed faraday cage.
The other answer about magnetostriction is technically correct (the best kind) but Misses the actual cause, which is subharmonic oscillation. This occurs when you have not stabilized your control loop properly and is often the result of inadequate phase margin. A simple fix may be to allow the control bandwidth by increasing capacitance at the work amplifier output. But this may also make the response too slow.
For most people designing DCDC converters, this is the most difficult part to understand and correctly tune. If you get the parts selection right and carefully lay out the circuit, this is the one that they can't get right. It takes some understanding of control theory or careful testing and tweaking. And it's what drives a lot of folk to the expensive and relatively inflexible power modules.
Noise can also come from pulse-skipping mode of regulation, if you draw too little power from the DC-DC converter, and can go away under higher load.
Yes. This is why the good ones have more parts. It's a totally fixable problem, and the parts cost to fix it isn't high, but it takes extra engineering effort.
All true, but for a hobbyist it probably isn't worth it if their goal is to just build some little audio project.
You are right. Yet, if you asked me how to get less noise on your audio circuit the LDO is the easier answer that will cost you less time to implement and likely give you the superior result.
Especially for beginners without a ton of measuring equipment and experience having potentially bursty high frequency components in series can be an interesting way to not get the thing they were planning done, but instead have to deal with an entire new set of problems whose existence they didn't even know about.
Technically you are correct, but "just slap a LDO on it" is probably the better advice.
And 3.3/5 is approximately 66% efficiency, which isn't too horrible. So even if you get your buck converter working, getting those 95%+ efficiency numbers you see in datasheets out of the circuit is not trivial.
> On the other hand, buck converters require you to actually do some actual engineering. You can't just haphazardly throw in a single IC and expect it to work flawlessly on your first try.
It used to be a hassle a few years ago - but these days you can haphazardly throw in a R-78K3.3-0.5 - which has the pinout of a classic three-pin 3.3v linear regulator, but it's actually an 80% efficient DC-DC converter with 500mA output and an input range that goes up to 36v.
That's enough current even if you've got something like an ESP32 that needs 250mA - and for any type of hobby project, the $2.40 is fine.
If you have 5V and have to step down to 3.3V using an LDO is a very reasonable choice (at 100mA you have about 170mW losses). However if you have e.g. 24V and need to step down to 3.3V, an LDO can get annoyingly hot (at 100mA you now have over 2W losses). But I agree, this is really a "it depends" situation.