Application bulletin from Precisionmircodrives on powering vibration motors from different and some cases fluctuating power sources. Link here (PDF)
As vibration motors have a wide variety of applications, they are often integrated into systems which have different power sources. A common concern, in terms of power supply, is adjusting the source power supply voltage to a suitable level for the vibration motor or drive circuitry. This protects the motor, and can ensure a constant level of performance for uses like haptic feedback.
from Dangerous Prototypes https://ift.tt/2vYRv1u