Need to control some stepper motors? The TI DRV8811 bipolar stepper motor driver is a simple solution but it poses an interesting problem - how do you decide what values to use for the passive components? In a recent blog post Jose Quinones of the Dallas Personal Robotics Group explains the problem:
Selecting these components is not a trivial endeavor. Make them too big and your switching frequency is too slow, with a high pitch squaling noise making your life miserable. Make them too small, and the switching losses increase, removing total power dissipation capability from the H Bridge’s power FETs. We need to match these values as close as possible to the optimal set of parameters in order to maximize our output.
Fortunately, Jose's blog post goes on to provide some helpful notes on selecting the R C values you'll need. He explains in detail how the current regulation engine works and how to compute the TBLANK and ITRIP parameters. He's got plenty of schematics and diagrams too. Jose should know what he's talking about because he's designed a stepper controller based on the DRV8811.