Last year I bought some KIS-3R33S 3A DC-DC step-down power modules based on the MP2307. (Link is to eBay seller Bosity’s current listing of this item. This is the seller that I ordered it from. A search on eBay for KIS-3R33S is available here.) This is a DC to DC power converter module that by default converts an input voltage of 4.75 to 23 V DC to 3.3 V DC, supplying up to 3 A (constant load).
You may need or want an output voltage other than 3.3 V DC, and you can, by connecting the Vadj pin through a resistor to either ground or Vout. Using Maxima and information from Digole and other pages I came up with formulas for calculating the proper resistance to use for any desired output voltage using an unmodified KIS-3R33S module.
The output voltage of the MP2307 is 0.925 * (R1+R2)/R2 (according to Digole, confirmed by datasheet from the manufacturer, MonolithicPower), where R1 is connected to Vout and R2 to GND. The unmodified KIS-3R33S module has two 51K resistors in parallell as R1 and one 10K resistor as R2 (giving us a theoretical actual output voltage of 3.28375 V DC). The module’s Vadj pin has a 3K3 resistor that will be in series with whatever you choose to connect to the Vadj pin.
For an output voltage higher than 3.3 V DC you want to connect the module’s Vadj pin through a resistor to GND. The output voltage using added resistance R will be (2627*R+27539100)/(800*R+2640000). To find the required resistance R needed to achieve output voltage V you would use R=-((2640000*V-27539100)/(800*V-2627)). For an output of 5 V you would want an external resistance of 10443.62709395484, Using standard E12 series resistors a single resistor of 10K would be close (theoretical Vout of 5.057246240601504), and you can get closer using a 10K in series with a 390R (theoretical Vout of 5.006722972972973, which is actually a much higher precision than that of standard 5 % resistors).
For an output voltage lower than 3.3 V DC you would connect the Vadj through a resistor to Vout. The output voltage using added resistance R should be 0.925*((1/((1/51000)+(1/51000)+(1/(R+3300)))+10000)/10000), and the resistance needed for an output voltage of V should be -((23040000*V-27539100)/(800*V-2627)). For an output voltage of 1.5 V you would use an external resistance of 4920.042046250876 connected to Vout. Using E12 series resistors that would probably mean a 5K6 for 1.535 V or 4K7 for 1.488 V.
So far I have not tested any of this IRL—caveat emptor!