Depending on the quality of the source signal provided to the DRV8662, an input filter may be required. Some key factors to consider are whether the source is generated from a DAC or from PWM and the out-of-band content generated. If proper anti-image rejection filtering is used to eliminate image components, the filter can possibly be eliminated depending on the magnitude of the out-of-band components. If PWM is used, at least a 1^st order RC filter is required. The PWM sample rate should be greater than 30 kHz to keep the PWM ripple from reaching the piezo element and dissipating unnecessary power. A 2^nd order RC filter may be desirable to further eliminate out-of-band signal content to further drive down power dissipation and eliminate audible noise.