Part Number:DRV11873
Greetings. I am using a DRV11873 in a custom design. It is driving a small Maxon motor (EC20 flat) at 12V. It generally works as expected, but at certain duty cycles, the driver will cut out, remain off for a few seconds, restart and continue this oscillation until the duty cycle is changed. For example, in my current design, if the duty cycle is set to 81%, the driver works without issue. If set to 82 or 83%, the driver cuts out/oscillates. In these conditions, the motor current draw in in the sub 600mA range. RPM is around 6500-7000 - the FS pin is pulled high. Any ideas regarding what might be causing this? Certainly it should not be an overcurrent or thermal issue. I need to investigate if the motor lock pin is toggling, but certainly the rotor itself is not physically being stopped when these oscillations are occurring
Note that the PWM frequency is set to be 25kHz, which is within the 7-100kHz spec per the datasheet.
Also note that I've experienced this oscillation in the past when using the drv11873 dev board as well.
If I change the loading on the motor when the oscillations are occurring, I can get them to stop. Any ideas about what might be happening? Anything I should be investigating to attempt resolve? This is a somewhat high priority issue since we are moving in to production with this design - rapid feedback appreciated.
-Chris