DRV2605L: motor vibration strength control

Hi, Sydney:

     I can control the motor to vibrate now, but the strength seems not strong enough, I tried all 123 waveforms and selected a stronger one, but still not very satisfied with it, then I tried to increase the Vrms value to 2.8v(the motor Vrms is 1.8v) which is used to calculated and used in rated voltage register, a little better, so I wonder if there're any other means to stronger the vibration?

    Thanks

    Bill