I am looking at the schematics for Makerbase TMC2226 stepper driver board:
The schematic shows 1/8W 0.11 ohm current sense resistors.
The datasheet for TMC2226 IC says:
8 Selecting Sense Resistors
... A 0.5W type is sufficient for most applications up to 1.2A RMS current.
The same section states that a current sense resistor of 0.12 ohm should be used for RMS current of 1.64A, and 0.1 ohm for 1.92A. 0.11 ohm is in-between.
The datasheet suggests 1/2W resistor for 1.2A, and the schematic shows 1/8W resistor for current greater than 1.64A.
How do these resistors not burn out? Is this just a bad board design, or does the datasheet sandbag power dissipation ratings? Or neither?
The actual board looks like this:
