PWM on DRV8838 driver board

I want to PWM control a small motor at low voltage (2xAA) with reversing control, 0.5A.

My question is about the PWM with this motor. Using the Enable input, it would seem to switch between power (in the selected direction) and braking (grounding both motor leads and dissipating any momentum). That seems like a very inefficient way to drive a motor. (The 8837 would allow one to PWM between drive and coast/HiZ, which seems more appropriate).

I’m wondering if using PWM on the nSleeep input of this chip would work to drive the motor, varying the proportion of time in drive and coast? That is, set Enable high and Phase to the desired direction, then drive the sleep input with PWM. I’m not sure if that input is compatible with PWM frequencies, or if my analysis (avoid braking the motor during the off size of the PWM cycle) is correct.


Sending a PWM signal to the nSLEEP pin might not be appropriate. According to the DRV8838 datasheet, there is a wake up time associated with that pin, and it can take up to 30 us before the IC is active.

Drive/brake operation is a common way to control DC motors. We generally recommend drive/brake operation over drive/coast since it provides a more linear relationship between PWM duty cycle and motor speed and usually results in better performance at low duty cycles. If you are still looking to operate your motor in drive/coast mode, you might consider our DRV8835 dual motor driver carrier. It can do both drive/coast and drive/brake operation.

- Jeremy