Electronic – Switch-mode power supply, and output voltage range – unregulated

In general you can assume that as long as the ripple is not too bad on a supply then it shouldn't cause an issue for functionality of an IC. In this case the datasheet gives a ripple of 100mV peak-to-peak, BUT you seem to imply that you're taking this voltage and further regulating it down. Passing a signal with a relatively small ripple and putting it through a linear regulator like a 7803 or an LDO will significantly reduce the ripple and cut back on switching noise passed through to the final circuit. So a ripple which is less than 5% of the expected voltage like this, being passed through a second line of regulation, should be fine for 95% of projects, even one using analog components like an ADC. Just make sure to have input and output filtering capacitors on the linear regulator, and not too much (2200μF is the limit for the power supply you gave) (maybe 47uF and 4.7uF (or 220uF and 22uF if you want it really smooth)).

Because the ripple is so small this supply would probably be fine for digital operations if you were using a 5V compatible chip and you weren't doing Analog work, but I digress.

So looking at the datasheet you provided, the operating frequency of the power supply is 132kHz. The chances that the noise from that is going to manage to produce harmonics in the 2.4GHz spectrum is pretty limited, especially at such small power outputs. Where you really have to start worrying about generated EMI is when you have isolating switching supplies, because these will pass power through the magnetic field, and the interface leaks EMI on most supplies I've used. Generally the higher-power the switching power supply the more noise it generates. I've had a 100Watt isolating switching power supply which put so much noise out I had 30V of noise on the frame of my robot, but that's way beyond the scope of this. I think you'll be fine with your usage!

Hope that helps!

Let me give you a little background on myself... I've been working professionally in the audio industry for more than 14 years. I've designed circuits for most of the major pro-audio companies, one audiophile company, and several consumer audio companies. The point is, I've been around and know a lot about how audio is done!

SMPS can and are used for audio circuits! I've used them from sensitive microphone preamps to huge power amplifiers. In fact, for the larger power amplifiers they are mandatory. Once an amplifier gets over a couple of hundred watts then the power supply needs to be super efficient. Imagine the heat produced by a 1000 watt amp if it's power supply was only 50% efficient!

But even on a smaller scale, the efficiency of a SMPS often makes a lot of sense. If the analog circuitry is properly designed then the noise from the power supply gets rejected by the analog circuitry and doesn't impact the audio noise (very much).

For those super-noise-sensitive applications you can do a hybrid approach. Let's say that you have an ADC that requires +5v. You can use a SMPS to generate +6v, then a super-low-noise linear regulator to bring that down to +5v. You get most of the benefit of the SMPS, but the low-noise of the linear regulator. It is not as efficient as just a SMPS, but those are the trade-offs.

But one thing to keep in mind... A SMPS for audio applications needs to be designed with audio in mind. Of course you'll need better filtering on the output. But you will also need to keep other details in mind. For example, at very low current the SMPS might go into something called "burst mode" or "discontinuous mode". Normally a SMPS will switch at a fixed frequency, but in one of these modes the switching will become somewhat erratic. That erratic behavior might push the output noise into the audio frequency band where it becomes more difficult to filter out. Even if the SMPS is normally switching at 1 MHz, when in one of these modes you could get 10 KHz noise. Controlling how this happens depends on the design of the chip that the power supply uses. In some cases, you can't control it. In that case you have no choice but to use a different chip or use a hybrid approach.

Some people advocate using only linear power supplies for audio. While linear supplies are less noisy, they have lots of other issues. Heat, efficiency, and weight being the biggest ones. In my opinion, most of the people who preach linear supplies only are either misinformed or lazy. Misinformed because they don't know how to handle switching supplies or lazy because they don't care to learn how to design robust circuits. I've designed enough audio gear with SMPS to prove that it can be done without too much pain.