Suggestions for a low noise stepper motor driver

Tanya42

I am currently using the DRV8825 (https://www.oyostepper.com/goods-887-5PCSPack-DRV8825-Stepper-Driver-Module-with-Heat-Sink-for-3d-Printer-Reprap.html) in some prototype electronics that include sensitive analog imaging electronics. The noise level of the imaging system is in the 10 μV range and my stepper motor drivers are injecting noise through the common PSU. Now, I did design the circuit correctly, using a good LDO to power the imaging sensor, using ferrite beads and plenty of decoupling, but there is some noise coupling there.

I do have some ideas on how to improve this from a PSU architecture perspective, but I wanted to explore the idea of ​​a linear stepper motor driver driven by a high frequency PWM generated by an FPGA that is filtered to a sine wave. This would drive a class AB amplifier stage or buffer for the stepper motor. The motor is a small NEMA 11, running at reasonable RPM and very light load, so it only consumes 1-2W.

Ideally, I'd like this circuit to be around $2 in 1k quantity. I think the best route might just be some discrete transistors in a class B setup. Does anyone have experience with this? Is this something a fool would do?

Thanks!