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DRV2605L: Amplitude Tracking

Part Number: DRV2605L
The question I have is in relation to tracking an LRA motors amplitude response with the driver when the driver is in closed loop PWM mode. It seems that with closed loop mode enabled, I will be able to track and report the LRA's resonance frequency and communicate it back to my MCU over the I2C bus.
I was wondering if there is a way that I can track the acceleration of the LRA motor with the driver and communicate it to my MCU over I2C. Is there a way to report the back EMF and therefore the acceleration of the motor via I2C?
  • Hi Lidong,

    The only back EMF reporting that is available is Register 0x19 which reports the back EMF of the resonant frequency at the rated voltage output during auto calibration.

    In terms of back EMF over frequencies, that is not available.

    Best regards,

    Jeff McPherson

  • Thank you for this response. Ok, so it sounds like back EMF can only be read during auto calibration, but not during regular operation of an LRA.
    Right, we are only intending to drive the actuator at resonance. 
    How would we go about measuring the acceleration of the actuator we are driving? Could we implement an RC circuit as shown, or would we need to understand the current that the actuator is pulling as well?
  • Hi,

    The test set up in Figure 11 will show you the voltage across the LRA, but it won't translate well to acceleration. If you want acceleration you'll need an accelerometer. While TI does not provide an accelerometer chip you can get the DRV-ACC16-EVM to measure your acceleration, with a direct correlation between G force and voltage output from the EVM.