I designed the stepper motor driving using DRV8811 driver from TI. The driver circuit is followed the recommended setting and made reference to DRV8811 EVM. The circuit is working fine at normal condition but the unacceptable performance happened when electrical fast transient bursts is coupling to power supply for immunity test. The motor is supposed to stop after turning 75 turns (designed with software control) even though there is power for driver and microcontroller. Now, the motor is slowly moving step by step according to coupling transient bursts input to the power supply. If the design is described roughly, VM supply is 24V, which is the main supply for the whole board. I used one rectifier between the main supply and VM for reverse polarity protection.There is 3K rating TVS on the main power supply and I also tried to use the suppressor to VM supply line but the problem is still there.
Now, the problem looks like somehow something trigger to turn "ON" the H-bridge when there is coupling transient bursts in the main power supply without STEP controlling from microcontroller. According to software controlling on STEP pin, the motor is supposed to stop. I have no idea where this interference comes from and what is the thing enable the H-bridge. I need to confirm the modification for this problem next week. So, could anyone help me to this issue?
