The HT878T is a stereo Class D audio amplifier that drives up to continuous 2×6.8W (1% THD+N, boosted to 8.3V) into 4ohm speaker. It also integrates Class AB amplifier to avoid EMI.
HT878T built-in Class G boost converter supports adjustable boost voltages. The boost converter is automatically active only when a higher audio output power is required, which will significantly improve the efficiency and extends the playing time in battery supply applications.
HT878T integrates Limiter function. When it is active, the output music can be limited below a certain power and THD+N. This will allow different demands in sound performance and prevent speakers from damage.
The Thermal Foldback (TFB) function is designed to protect the HT878T from excessive die temperature in case of the device being operated beyond the recommended temperature or power limit, or with a weaker thermal system than recommended. The TFB works by reducing the on-die power dissipation by reducing Gain if the temperature trig point is exceeded, so that the peak audio power is significantly increased.
HT878T has a filter-less modulation circuit which can directly drive speakers. HT878T can be shut down so that the power consumption can be minimized. 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.
Power ground. Also provides thermal connection from the device to the board. A matching ground pad should be provided on the PCB and the device connected to it via solder.
Adjustable switch peak current limit. An external resistor should be connected between this pin and GND.
Error amplifier output. Connect a 3.3nF capacity paralleled with a 15k resistor to GND typically.
Boost and rectifying switch input.
Power supply for logic.
Positive input (differential+) for audio amplifier of left channel.
Negative input (differential-) for audio amplifier of left channel.
Negative input (differential-) for audio amplifier of right channel.
Positive input (differential+) for audio amplifier of right channel.
Audio amplifier mode selection. Class D is selected when it is pulled low; Class AB is selected when it is pulled high.
MUTE control set. The audio amplifier is muted when it is pulled high.
Enable the Limiter Function and select limiter level.
System GAIN set. Three GAIN level for select.
Positive output terminal (BTL+) for right channel.
Power supply terminal for right channel.
Negative output terminal (BTL-) for right channel.
Negative output terminal (BTL-) for left channel.
Power supply terminal for left channel.
Positive output terminal (BTL+) for left channel.
Audio amplifier enabling terminal. Audio amplifier is enabled when it is pulled high.
Boost converter enabling terminal. Boost converter is enabled when it is pulled high.
Regulator Feedback Input.
Boost Converter voltage detect pin.
I: Input; O: Output; G: Ground; P: Power