Question about A4988 Rsense value

I’m curious how you arrived at the 0.068/0.050 values for Rsense. According to my math this puts Vref at 1.088/0.8 for the maximum 2.0A setting. This will have the current control DAC operating in the lower 25% of its useful range. For applications with much lower current requirements, this puts the control way down in the mud where accuracy is dubious, at best.


The resistances are approximately the limits for the 0805 size resistors: 50 milliohms for 1/4W and, more recently, 68 mohms for 1/3W. (This means that knock-offs of our boards using smaller resistors or bigger resistances are violating their resistor ratings.)

By the way, we offered higher and lower current versions with the DRV8824/DRV8825 stepper motor drivers, and the sales were close to 20:1 for the higher-current versions, so there does not seem to be much interest in drivers optimized for lower currents. If you have an application with higher volumes, we can make some of the boards for you with bigger resistors. Please let us know if that is something you would like to pursue.