The PAM8904 is a 1X/2X/3X Piezo Driver capabable of 1X/2X/3X Boost modes with an input of 1.8-5.5V.  The smPWR-PAM8904 provides a micro-sized breakout board measuring 20.4x12.7mm for the PAM8904 and provides jumper pin selections for the 1X/2X/3X modes and oversized solder pads for connecting a piezo speaker/buzzer. Additionally the device has excellent built in features such as Automatic Standby Operation and Wake-Up-Control.  Use the Open Source BLE Controllable Firmware and Flutter App to test the smPWM-PAM8904. nRF52/nRF52840 DK BLE Firmware:  smPWM_BLE_nRF52 Firmware Flutter App controls DUTY_CYCLE and FREQUENCY:  smPWM_BLE-Flutter