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ST FDA series Class-D Audio Amplifiers for Automotive Application

Dec 14 2022

With the development of electric vehicles, new application scenarios are constantly being proposed. Class-D audio amplifiers meet the energy efficiency, design flexibility, and reliability goals of electric vehicles. STMicroelectronics released FDA803S and FDA903S, automotive audio power amplifier chips, which bring flexible digital signal processing functions to e-Call, telematics and AVAS.

FDA803S and FDA903S for Automotive Application

The FDA803S/903S is a single-channel fully differential 10W Class-D audio power amplifier, which is a new product in the second-generation FDA series of STMicroelectronics. Integrates an I2S front-end circuit, a digital core, a 100dB resolution 24-bit digital-to-analog converter (DAC), and a Class-D PWM output stage. The internal feedback circuit of the chip is placed in front of the external L-C output filter, which simplifies the circuit design and saves space. In addition, an on-chip digital audio processor ensures that the amplifier can achieve high sound quality in a small area.

ST Audio power amplifier - FDA903S and FDA803S

Source: STMicroelectronics

On the package, it adopts QFN32 5mm x5mm exposed pad down package, which can realize compact and cost-effective all-digital design without the need of heat sink. Low component count and no heatsink implementation minimizes the size of power amplifiers built with these ICs. In addition, it has the advantages of low quiescent current, light weight and low power consumption, which help to improve the overall energy efficiency of the vehicle.

If you want to minimize external components and BOM costs, these two will be a good choice. They all integrate a full I2C configuration function and on-the-fly diagnostics, including clipping detection, overheating warning, overcurrent protection, and open load detection. The FDA903S also integrates a real-time load current monitor, allowing self-diagnostics compatible with the needs of functional safety applications up to ASIL A.

Both the FDA803S and FDA903S feature an I2S digital input and a time-division multiplexed (TDM) interface. They can be configured for various sampling frequencies between 8kHz and 96kHz to optimize the performance of various audio sources. The lower sampling frequency from 8kHz to 32kHz enables designers to save memory space in applications such as warning tone generators.

Audio Amplifier Brings Better Safety to Electric Vehicles

The target applications of ST's FDA903 series and FDA803 series are automotive audio systems. The difference is that FDA903 adds a current detection function specially designed for high-end models. These two series include D, Q, U three kinds of products, respectively adopt PowerSSO 36 pad down, VFQFN 48 and PowerSSO 36 pad up package.

The working principle of the audio amplifier is to receive and process the input audio signal, convert the digital signal into an analog signal, and output it to the speaker. For electric vehicles, energy saving is the key to extending the cruising range. Therefore, in addition to avoiding signal distortion as much as possible, audio amplifiers also need to ensure that power consumption is as low as possible. Class D power amplifiers have an energy efficiency higher than 90%, which can perfectly meet the needs of electric vehicles.

ST's FDA series of amplifiers supports a wide-voltage power supply, so the amplifier can be powered from a car battery, an external step-down converter or a small battery. So even after the car battery is exhausted, the amplifier can still sound an alarm or prompt to remind the driver to pay attention.

In addition to automotive applications, small speakers for consumer products often have limited consideration for Class D audio power amplifiers. Thanks to its small package, which helps to reduce the size of the application system, coupled with its high energy efficiency and low heat generation, it can also be installed in hearing aids.


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