Automotive audio power amplifiers for eCall, telematics, and AVAS

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By Jean-Pierre Joosting

Designed for automotive applications, the FDA803S and FDA903S are the latest single-channel fully differential 10-W Class-D audio power amplifiers in the STMicroelectronics FDA (fully digital amplifier) family. The power amplifiers are suitable for applications like eCall, telematics, and wherever an audio channel needs to reproduce human voice, music, or warning messages at a standard output power level of up to 10 W.

The amplifiers integrate an I2S front end, digital core, 24-bit digital-to-analog converter (DAC) with 100 dB resolution, and class-D PWM output stage. The integrated digital audio processing ensures high sound quality within a compact circuit footprint. Feedback within the chip, before the external L-C output filter, simplifies the circuit design and saves space.

With full I2C configurability and in-play diagnostics that include clipping detection, thermal warning, overcurrent protection, and open-load detection, both amplifiers minimize external components and bill-of-materials costs. The FDA903S additionally integrates a real-time load-current monitor, allowing self-diagnostic capability compatible with the demands of functional-safety applications up to ASIL A.

Both devices come in QFN32 5- x 5-mm exposed pad-down packages that enable a compact and cost-effective, fully digital design without the need for a heatsink. The low component count and heatsink-free implementation minimize the bulkiness of power amplifiers built using these ICs. Also benefiting from low quiescent current, the opportunity to minimize size, weight, and power consumption contributes towards improving overall vehicle energy efficiency.

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

The EVAL-FDA903S evaluation board gives designers a jump-start to new audio projects based on either device and is available for $189.88. The FDA803S and FDA903S are in production now.


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