HT8691 integrates a boost converter with a filter-less stereo class D audio power amplifier to provide 5.5W continuous power into a 4Ω speaker when operating from a Li-battery voltage boosted to 6.5V, 7.0W continuous power into a 3Ω speaker when operating from a Li-battery voltage boosted to 7.0V. Meanwhile, the boost output voltage is adjustable.
HT8691 features Anti-Clipping Function (ACF) which detects output signal clip due to the over input signal and suppresses the output signal clip automatically. Also, the ACF function can adapt the output clip caused by power supply voltage down with battery. It can significantly improve the sound quality, creating a very comfortable musical enjoyment, and to protect the speakers from overload damage. It also supplies ACF OFF mode.
Class AB amplifier mode is also available for HT8691. Once the EMI Interference from class D and Boost Converter becomes an annoying problem, HT8691 can be changed into Class AB mode.
HT8691 has a filter-less modulation circuit which directly drives speakers while realizes low distortion and low noise characteristics. Thanks to filter-less, circuit design with fewer external parts can be made in portable applications.
HT8691 has the independent Shutdown function which can minimize the power consumption at standby and MUTE function. As for protection function, over current protection function for speaker output terminals, over temperature protection function, and low supply voltage malfunction preventing function are also prepared.