6 How to Measure Auto-Resonance

The question that often arises is “How can I measure the auto-resonance frequency?” Measuring the frequency is quite easy. To see what frequency the DRV260x or DRV262x family of devices is driving, measure the filtered PWM-modulated output waveform or alternatively in both families of devices a register holding a LRA_PERIOD byte can be translated using a mathematical formula provided in the data sheet to tell users what the given output frequency is operating at. But filtering the output waveform will allow users to see the underlining sine or square wave. See the DRV2605EVM-CT User’s Guide or DRV2625EVM-CT User's Guide for more information on filtering.

Measuring the output frequency can be clear, but How do I know that the DRV260x or DRV262x drivers are driving at the resonant frequency? The answer is, Users can see if device output frequency matches LRA's data sheet value but the exact resonant frequency cannot be determined entirely empirically because of the many environmental factors. It is easier to answer a different question: Is the performance better with auto-resonance tracking? The answer is yes. Auto-resonance dynamically tracks the LRA frequency to improve acceleration, efficiency, and braking time.