DC-DC Converter with MAX756
[Update 24.04.2021 – KiCad PCB]
Sometimes I need a stabilized power supply, as example for the sound meter project. I think best solution for me is an MAX756. That circuit doesn’t need so much external components and can suck out one (or more) batteries down to a minimum voltage of 0.7V, almost until the last free electron.
The MAX756 can deliver 3.3V/300mA or 5V/200mA. There is also the MAX757 version, allowing output voltage free adjustable. Without load the circuit consumes only a little over 80µA as I measured. There are SMD versions of course, but one packaging version is an 8 pin Plastic DIP = super easy handling.
So I designed an strip pcb with an voltage “programming” connector for easy switching. If you don’t need that as part of your project – just hard wire the connections for 3.3 or 5V. Of course you can also leave out the socket and solder the circuit directly to the board, which improves the long term stability of the assembly. BTW – you can download the package of all files: MAX756_3.3-5V Powersupply.zip
You may mount/glue the battery pack of the copper or parts side. I prefer the copper part, because it separate this from my table which is usually covered with rests of wire and solder. That helps to avoid short circuits.
The voltage selecting plugs:
So feel free to use my strip PCB design for your own projects – license for the pcb is CC BY-SA 3.0
Update 24.04.2021 – KiCad PCB
I used that design in the last time a few times. In addition I started with KiCAD, so I created a PCB. The outer dimension fit to the backside of a typical 2AA battery holder.
Download: