spacer 5V Boost Switching Regulator

Here's a little project I put together for a friend. He wanted to build a project that ran off 5V but didn't want to use a 9V battery. I found an interesting part on Digikey that can take the output of 1 or 2 AA or AAA batteries and boost it to 5V. Infact the part can be programed for any output voltage between 1.8V to 5.0V using two resistors. If you leave off the resistors you get a 3.3V output. Best of all the PCB fits onto the end of the battery holder. Sweet.

One drawback is that at 5V output the part only puts out about 200mA with two AA or AAA batteries. It drops lower to about 50mA with only one cell. On the other hand, if you use 4 cells, you can approach 500mA.

The other drawback is that the part comes in an SOT23 package which is pretty tiny. My old eyes can still solder this so perhaps you can too.

Regulator fits on end of dual AA or AAA holder

The board is designed to slip over the terminal of a dual AA or AAA battery holder. The solder tabs are bent at right angles and rotated to the outside. A little bit of solder holds the board in place. Be careful not to melt the plastic of the battery holder by applying heat for too long.

Board view of regulator

Here a parts list of what you'll need. Prices are approximate. The datasheet recommends using X5R or X7R 22uF capacitors. Also I would recommend using 0.1% resistors. I used 1% and my output voltage on a test board was 5.14V.

Qty Digikey Part Description Price
1 SC120SKCT-ND IC BOOST 3.3V/ADJ SOT23-6 1.24
1 445-6760-1-ND INDUCTOR 4.7UH 0805 0.12
2 587-2782-1-ND CAP CER 22UF 10V X7R 20% 1206 1.20
1 RMCF1206FT590KCT-ND RES TF 590K OHM 1% 0.25W 1206 0.05
1 RHM1.87MFCT-ND RES 1.87M OHM 1/4W 1% 1206 SMD 0.05
1 311-1154-1-ND 22pF 1206 SMD 0.13
1 BC22AAL-ND AA 2 cell holder 0.75
1 BC2AAAL-ND AAA 2 cell holder 0.75
  Total ~$3.50 plus a PCB  

The links below lead to a printable PCB suitable for making the PCB via toner transfer. It's ready to iron. The other link shows how to assemble the board.

Thumb of the PCB  Thumb of assembly instructions  Thumb of Schematic