You’ve just finished the block-diagram version and maybe a rough schematic of your new design. There are some op amps, maybe some analog switches, a voltage reference or two, some other analog interface ICs, a couple of A/D or D/A converters, and some power management. Now you need to pick the components that together will meet your performance and cost objectives. Maybe you’re constrained to use only the chips that are available in your CAD library, on a qualified-products list, or maybe you are free to u
Source: EDN – How to read a data sheet