Current based resonant frequency tracking system

A method of operating a current based resonant frequency tracking system comprising:

• providing a haptic pattern with a processor, the haptic pattern concluding with a haptic pattern stop time;
• driving a linear resonant actuator according to the haptic pattern with an amplifier coupled to the processor, and the amplifier having an output coupled to the linear resonant actuator;
• detecting a current sense signal having a back electromotive force current after the haptic pattern stop time with a current frequency tracker coupled to the output of the amplifier;
• measuring a frequency of the back electromotive force current as a resonant frequency of the linear resonant actuator;
• and
• detecting cycles in the back electromotive force current after the haptic pattern stop time.

A current based resonant frequency tracking system comprising:

• a processor configured to provide a haptic pattern, the haptic pattern concluding with a haptic pattern stop time;
• an amplifier coupled to the processor, the amplifier having an output configured to couple to a linear resonant actuator and configured to drive the linear resonant actuator according to the haptic pattern;
• and
• a current frequency tracker coupled to the output of the amplifier configured to detect a current sense signal having a back electromotive force current after the haptic pattern stop time, and the processor configured to measure a frequency of the back electromotive force current as a resonant frequency of the linear resonant actuator.