Class-D digital PAs for a better in-car audio experience
ST’s second-generation FDA801 and FDA801B 4-channel class-D amplifiers with digital input convert the digital audio source directly into high-quality sound. The digital input gives immunity to GSM noise, improves sound quality, saves component costs, and simplifies system design. ST introduced the 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 revolutionising 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.
These 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 step forward, ST asserts, in automotive diagnostics compared to any other audio amplifier.
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, in “ high volumes only” in a LQFP64 Exposed Pad Up package that allows efficient heatsink attachment.
Features include;
- 115 dB Signal to Noise Ratio (SNR); 110 dB dynamic range;
- Simplified digital input eliminates external DAC and external decoupling capacitor, thereby avoiding potential DC-offset problems;
- More than 40% power saving compared to standard class-D amplifiers;
- Digital Impedance Meter (DIM, in FDA801B) automatically recognises magnitude and phase of the connected speaker and communicates it by digital bus (I²C);
- Internal 24-bit DAC conversion and very low noise in line-driver and amplifier modes ensure superior audio performance;
- On-demand advanced diagnostics allows each channel to independently perform AC or DC diagnostics with configurable parameters;
- Ability to drive loads down to 1 ohm gives designers complete flexibility to specify preferred speakers.
ST adds, “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 analogue-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.”
STMicroelectronics; www.st.com
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