The HT868 is a smart audio power amplifier with TFB, AGC technology and an integrated adaptive sync boost converter that enhances efficiency at low output power. It drives up to continuous 10W (3% THD+N, boosted to 8.0V) into 3ohm speaker, or instantaneous 2×6.5W (1% THD+N, boosted to 8.0V) into 4ohm speaker from a Li-battery voltage.
The built-in sync boost converter generates a supply voltage (6.5V, 7.5V, 8.0V optional to meet different out power demands) for the audio amplifier. The boost converter is adaptive and is automatically active only when the peak output audio signal exceeds a preset voltage threshold, which is optimized to prevent clipping while maximizing system efficiency. What more, there’s no need for an external diode.
HT868 integrates Automatic Gain Control (AGC), including Limiter and Battery Tracking function. When Limiter function is active, the output music can be limited below a certain power and THD+N. When Battery Tracking function is active, HT868 monitors the battery voltage and the audio signal, automatically decreasing gain when battery is lower than preset voltage and the audio output power is high. It finds the optimal gain to maximize the loudness and minimize the battery current, providing louder audio and preventing early shutdown at end-of-charge battery voltages.
The HT868 Thermal Foldback (TFB) is designed to protect the HT868 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.
HT868 has a filter-less modulation circuit which can directly drive speakers. HT868 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.
1. HT868 BTL MODE
2.HT868 PBTL MODE
Power ground for boost converter
Power supply for left channel
Terminal that enables and selects Battery Tracking Function for left channel
Negative input (differential-) for audio amplifier of left channel
Positive input (differential+) for audio amplifier of left channel
Parallel BTL mode switch
Power supply for right channel
Terminal that enables and selects Battery Tracking Function for right channel
Negative input (differential-) for audio amplifier of right channel
Positive input (differential+) for audio amplifier of right channel
Select boost converter output voltage VPOUT for right channel
Negative output (BTL-) for audio amplifier of right channel
Power supply terminal for audio amplifier of right channel
Power ground for audio amplifier of right channel
Positive output (BTL+) for audio amplifier of right channel
Select boost converter output voltage VPOUT for left channel
Negative output (BTL-) for audio amplifier of left channel
Power supply terminal for audio amplifier of left channel
Power ground for audio amplifier of left channel
Positive output (BTL+) for audio amplifier of left channel
Boost Converter output voltage
Boost and rectifying switch input
Connect to PGND
I: input O: output