U3V12F12 boost reg question

Here’s my situation. I’ve been working with some low power (10-20W) class-D audio amplifiers intended for automotive use. I’m using them to make portable low power guitar “practice” amps. The 12V category has a lot of inexpensive choices. I have also been experimenting with powering these amplifiers with various 3 cell Li-ION or Li-Polymer cell packs. These output a max of about 12.6V on full charge (4.2 x 3), and about 9.9V ( 3.3 x 3) near the end of what I’d call their useful charge life. The problem is that most of these automotive class D amps start to lose their sound quality at about 10.5V. So I’m not getting the full use out of my 3 cell packs. I could go for a 4 cell pack, but that would raise the full charge voltage above the abs. max of most of these amplifiers.

So… I’d like to use some kind of circuit that would offer closer to 12V over the voltage input range I’ve described ( 9.9 - 12.6). I also would need about 2.2 “peak” amps, assuming 100% efficiency from my class-D amplifier, outputting 20 w into 4 ohms.

I’m considering using two of you U3V12F12 boards, and perhaps paralleling the outputs, if that is allowed. If not, maybe you have a higher current version? 3 Amps would be more than adequate. I am also concerned about the tolerance of this board to slight over-voltage, because a fully charged 3 cell LIPO pack will briefly output about 12.6 V. If that slight over-voltage isn’t OK, I possibly could consider making a switch-over circuit, where the amplifier would receive direct battery voltage until the input dropped to maybe 11.0V, and at that point somehow make the switch. But that sounds like difficult task, especially considering that the switch-over would have to happen without interrupting the audio.

Anyway, that’s my situation. I’ve been a customer for many years buying other things (mostly wixels), and was very happy to find my google search for 12V boost regulators find your product. Hopefully I can use it! :slight_smile:


It is generally difficult to parallel regulators well, so we do not recommend it. For your case though, it looks like our S18V20F12 might work. The S18V20F12 is a step-up/step-down regulator, so it will give you a 12V output whether the battery voltage is above or below 12V, and it can handle peaks of about 2A over the voltage range you are interested in, though the maximum sustainable current is probably a few hundred mA less. You might also consider using a higher voltage battery and a step-down regulator like our D24V22F12 regulator.


Hmm… Well I think I’d better plan on 1 amp sustained for my situation.

I suppose i could buy a handful and try the parallel arrangement and do some load tests. Worst that could happen is I fry them, right? But then if I’m lucky, is they use power MOSFETs on their outputs, the slight resistance each presents might mitigate the situation and allow a parallel arrangement. Especially if I put a good size capacitor on the output, like a reservoir capacitor. But about the over voltage… just what is the abs. max input voltage? If it can tolerate that 1/2 volt extra, it might work. Do you have a spec for this?

The components on that regulator are rated to handle up to 16V on the input, so it probably won’t be damaged by applying 12.6V. The extra voltage will pass through to the output though.