STMicroelectronics introduces flexible, space-saving Class D amplifiers for automotive audio

     The ST HFA80A Automotive Scale proposed input Class D audio amplifier combines high energy efficiency, small size and low material cost with optimized load diagnostics for automotive and local electromagnetic compatibility (EMC). The HFA80A uses a pre-filter feedback topology and a 2MHz nominal PWM frequency, allowing designers to optimize the output filter according to the target performance, and use smaller external components during the design process to achieve a compact product design. The spread spectrum operation simplifies the mandatory CISPR 25 compliance process without the need to design additional EMC specific filtering circuits.

     The new amplifier delivers a clear, robust music listening experience, delivering up to 4x 49W of power to a 2Ω speaker at 14.4V with a typical harmonic distortion (THD) of 0.015% (1W/4Ω). The new power amplifier chip ensures pure speaker sound quality, low output noise and crosstalk, and a power supply voltage rejection ratio of 80dB when loading a 1W/1kHz input signal and a 4Ω load.

     The flat frequency response of up to 40kHz brings ample bandwidth for high-resolution audio, which designers can extend to 80kHz by optimizing filters. In addition, because of its low latency design approach, the HFA80A can handle applications that focus on performance, such as noise reduction.

     Vehicle-specific diagnostics are based on a specially designed anti-noise algorithm that detects abnormal conditions and changes in the load. Diagnostic features include direct AC load detection per channel, short-circuit detection at startup, and overcurrent protection with threshold setting. Other diagnostic tests include DC input voltage offset detection, output current offset detection, and overheat protection with the option of four different temperature warnings.

     The HFA80A comes with a configurable dedicated pin and I2C bus interface. When there is new diagnostic information, the special pin can be configured to send a signal to notify the main microcontroller. This design simplifies the communication connection between the power amplifier chip and the main controller, and reduces the computing load of the CPU. The master controller can control the power amplifier chip function through the I2C bus interface, access diagnostic data, even if the I2C control function fails, the backup mode allows the amplifier to continue to operate normally. In addition, the HFA80A is equipped with a digital admittance meter (DAM), which helps engineers check the characteristics of connected speakers without using external measuring tools or sensors, simplifying the development process.