How to optimise DRV8711 decay mode setting

High resolution micro stepping is widely employed in security cameras, CNC systems, stage lighting, and other applications requiring smooth movement. The DRV8711, which is a stepper motor controller with an integrated indexer, achieves step modes from full step to 1/256-step and is adequate to these high resolution applications.

The ideal sinusoidal winding current could match the magnetic natural characteristic of a stepper and assure the stepper to have a smooth and uniform movement in high degree micro-stepping. However, due to the different electrical parameters and different motors, there are always some difficulties in realising a perfect sinusoidal wave. The current profile is actually the result of the detailed decay settings. Since the DRV8711 gives the most flexibilty of decay mode configuration including slow, fast, mixed, slow+ mixed, slow+ auto mixed, and auto mixed 6 modes and related detail tunings, we chose the DRV8711 EVM to demonstrate the adjustment methods.

This application note analyses the decay adjustment methods to fix the typical abnormal waveforms of winding current. All the following adjustments attempt to just change one parameter at a time, such as off-time, blanking time, decay time, and decay mode, in order to give the clear trend of each parameter's change. In real applications, there could be a combination of parameters tunings to get the most optimised result with the least side effects.

View the PDF document for more information.

Originally published by Texas Instruments Inc. at www.ti.com as "DRV8711 Decay Mode Setting Optimisation".