Introduction

Design high-quality speakers, TVs, and soundbars with best-in-class audio amplifiers from Texas Instruments (TI). The amplifiers offer a wide range of advanced features and capabilities to enhance the overall listening experience. TI's Class-D amplifiers offer exceptional power density, efficiency, and thermal performance, making them an excellent choice for applications where space is limited or thermal management is critical. In this document you will find advanced features being used in everyday speakers, TVs, and soundbars enabling end customers a more immersive audio experience. See Table 1 for Audio Device Recommendations.

TI's Class-D amplifiers enable designers to:

• Improve system efficiency and reduce power consumption
• Minimize board space and thermal footprint
• Enhance reliability and extend product lifespan through advanced protection features
• Achieve higher audio fidelity with reduced distortion

Class-H Architecture

Figure 2 and Figure 3 show how Class-H control dynamically adjusts the supply voltage (PVDD) based on the audio signal. When the signal is small, PVDD is low, reducing power dissipation. When the signal is large, PVDD is increased to provide the necessary headroom without overstressing the switching devices. By minimizing the voltage difference between the supply and the instantaneous signal level, Class-H significantly reduces switching losses within the output stage, improving overall efficiency.

Figure 2 Audio Output and Boost Voltage Without Class-H Operation

Figure 3 Audio Output and Boost Voltage With Class-H Operation

Thermal Foldback

Thermal foldback is a power limiting feature (a type of thermal protection). The prime purpose of foldback power limiting is to keep the output stage within a safe power dissipation limit to avoid unexpected overtemperature shutdown (OTSD).

The audio DSP core uses the thermal foldback feature to monitor junction temperature continuously in real-time to provide safe operations. As the junction temperature rises above the threshold set by operating threshold warmup (OTW), the thermal foldback circuit initially activates. This scenario provides a smooth audio response and allows for uninterrupted music playback when OTW limits are crossed. That means the device simply does not shut down but continues to operate with considerable music output power to avoid triggering OTSD. See the TAS5825 Advanced Features application note for more details on Thermal foldback.

Cycle-by-Cycle (CBC)

Cycle-by-cycle (CBC) current limit is a protection feature that prevents the output current from exceeding a specific threshold during each PWM pulse. When the current hits the limit, the device limits the current for that cycle and continues operation without triggering a fault. This allows the device to handle large peak currents in short durations and continue operation without audio disruption by limiting the music signal peak power. This feature has many configurable options based on the desired result, there are registers you can toggle to enable faults and warnings or limit the overcurrent threshold by a percentage.

Table 1 shows the different audio device recommendations.