Avayan offers this great discussion of how to choose the passive components for the popular DRV8811 stepper driver, as well as some good insight into how the chip works. He writes: [via]
The DRV8811 is clearly a bipolar stepper driver that makes our lives considerably easier. It is just so simple to drive a stepper with this powerful device, as well as similar internal indexer microstepping engines, who takes care of all the nuances of phase commutation and current control. Just supply your stepping rate in the form of a square wave with the desired frequency and a direction signal, and WALAS! Your motor moves!
Choosing Components for the DRV8811 Stepper Driver – [Link]