This adjustable buck converter takes a higher voltage and efficiently cuts it down between 1.23~30VDC, without wasting the power a linear regulator or resistor will.
Especially in battery-powered situations, you want to waste as little power as possible. When you use an LM7805 or resistor to reduce voltage levels, you turn the extra power into heat, wasting it. Fortunately, the LM2596 is a clever little IC that works with a coil to efficiently reduce voltage levels efficiently, which extends battery life and makes your design run cooler.
So let's repeat that: This device only reduces a voltage to a new lower, regulated voltage. It won't' step it up (but there are other devices that will). Also, as good as it is, a characteristic of this design is that they are a bit noisier than a linear regulator. It's a great trade-off when you don't need a super-quiet, solid power supply that is either much more expensive, or power inefficient.
In short, the positives are:
The negatives are: