Digital power amplifiers for car audio deliver cleaner sound

ST's second-generation FDA801 and FDA801B 4-channel class-D amplifiers with digital input convert the digital audio source directly into high-quality, cabin-filling sound. The digital input gives immunity to GSM noise, improves sound quality, saves component costs, and simplifies system design. ST introduced the world's first class-D digital-input automotive-audio amplifiers in 2012, and is now moving forward with its new and improved second generation that will be soon completed with pin-compatible ICs in various multi-channel configurations.

"Class-D amplifiers are revolutionizing in-car audio throughout the marketplace, from audiophile systems in prestige vehicles to affordable, high-quality sound in smaller cars," said Alfio Russo, Group VP, General Manager Audio & Body Division, Automotive Product Group, STMicroelectronics. "ST continues to drive the pace of development, with these new chips setting even more advanced performance and efficiency benchmarks for the industry."

ST's new power amplifiers combine superior audio quality and increased energy efficiency, as well as the unique real-time measurement of speaker impedance via the new Digital Impedance Meter (FDA801B), which represents a quantum leap in automotive diagnostics compared to any other audio amplifier.

Key to these enhancements is ST's advanced fabrication process, BCD9s, which minimises interference between circuits on the chip, lowers standby-power consumption, and cuts power-transistor dissipation raising efficiency to more than 93%.

By dissipating less power, the FDA801/B can help boost fuel economy in conventional vehicles and extend the driving range of hybrids or battery EVs. Like their predecessors, ST's new amplifiers are compatible with fuel-saving start-stop technology, maintaining uninterrupted playback when the vehicle battery voltage dips as the engine is restarted.

The FDA801 and FDA801B are available immediately in the LQFP64 Exposed Pad Up package that allows efficient heatsink attachment. Pricing, for high volumes only, is available on request.

In addition to simplifying circuit design, the digital input and external feedback topology make the amplifier's frequency response independent of the load impedance and output-filter design. This allows easy scaling to create multiple product variants based on a common platform, without requiring detailed redesign of the amplifier. Unlike analog-input class-D amplifiers, the FDA801/B can be used in head units as well as booster amps thanks to superior noise immunity, lower switching interference, and lower power dissipation that permits smaller heatsinks.