DRV8889-Q1: Output current waveform consult

Hi Zhiyuan,

Thanks for posting this question. You said "In low input voltage(9V) and high step frequency (1.18Khz), the inductor current can not rise/fall on time.". It is not only because of the inductance of the winding. The bigger contributor is the back EMF. At high speeds the back EMF increases and reduces the available voltage to the coil and unable to push the desired current fast enough before the next step pulse is issued. 

1. Is this an issue? What is the risk? This is a common phenomenon while running steppers at high step rates and not sufficient VM supply voltage. As long as the motor does not stall, meaning sufficient torque is generated which should be true in this example, there is no major risk except having uneven step size with physical microstep movement.  

2. How to improve? The motor, step frequency and the input voltage are requirement from the customer and cannot be changed. In such situations the real remedy is to increase the VM. Because customer cannot reduce the step frequency and the VM voltage, the only option would be to reduce the IFS current setting to a point until the waveform improves. This would result with reduced torque. The engineer must determine if this reduced torque acceptable for their application.

Regards, Murugavel