The RT5509 is a mono BTL class-D amplifier with cutting-edge speaker protection algorithm. Also, a built-in DC-DC step-up converter is used to provide efficient power for class-D amplifier. I2S interface supports two different audio sources while a pair of auxiliary DATAI/O is used for stereo mode or pass-through application. Chip information including gain, speaker protection output or current sense is able to be monitored via DATAO through proper register setting. Speaker protection provides mechanical / thermal protection with accuracy of 10%/±10ºC of rated limit.