I have bought a Step-Down Voltage Regulator D15V35F5S3 and am trying to use it to power my raspberry pi from a 12V computer PSU.
The test is:
- connect the PSU to the D15V35F5S3
- check the output voltage (5V)
- connect the raspberry pi
- wait for it to boot
- play some mp3 music
When using a USB 1A phone charger I get clean sound. When using the D15V35F5S3 I get a lot of noise that seems to be coming from the regulator. I have measured the current drawn from the PSU and it never exceeds 250mA.
I will test with a 12V battery too but in the meantime do you have any idea what could be wrong?
In general, switching regulators can be noisy, and audio applications might require additional noise suppression. You might look into whether the noise is getting conducted in on the power lines or getting in electromagnetically. For the conducted part, you can see if putting various caps across the power lines helps (keep in mind that in this application, things like 0.1 uF in parallel with 2.2 uF and 100 uF is not the same as a single bigger cap because different kinds and sizes of caps will be better for different frequencies). To check for how much the non-conducted noise is an issue, you can try moving the regulator and raspberry pi relative to each other to see how that affects the noise. In some cases, just a few inches can make a big difference if you happen to have them in a particularly unfortunate arrangement.