Mixed Signal/Analog

New audio amplifiers feature second generation multilevel switching amplifier tech

22nd November 2022
Paige West

When designing portable and battery-powered audio devices for consumer speaker applications, maximising battery playback time and, at the same time, maintaining excellent audio performance in a compact form and at a low system cost is essential.

MERUS multilevel switching technology from Infineon Technologies is designed to achieve low switching losses and highly efficient amplification at both low and high output power, bringing the desired benefits in such applications. The new ICs feature the second generation of this technology and come in a compact 40-pin QFN package. They primarily address applications such as battery-powered speakers, Bluetooth/wireless/smart speakers and soundbars, conference speakers, and multi-channel/multi-room audio systems.

The new family consists of MA2304DNS with an integrated and fully-configurable digital signal processor (DSP) and MA2304PNS with audio limiter and volume control features. Both devices feature the second-generation multilevel-switching class D audio amplifiers with an inductor-less operation and provide a bridge-tied load (BTL)- rated output of 2 x 37W and a power supply voltage range (PVDD) of 10 to 20V for high fidelity audio performance. The five-level voltage modulation offers an ultralow idle power of 52mW without the need for complex dynamic rail‑tracking systems. This is at least five times lower than the traditional class D audio amplifiers, making these devices ideal for battery-powered speaker applications with extended battery life and/or reduced battery cell cost.

At low output power, the efficiency can be higher than 80% offering extended battery life and easy thermal management in multi-channel products. Multilevel switching also relaxes electromagnetic compatibility (EMC) requirements and enables inductor-less applications at full power range with lower cost. Compared to traditional two- and three-level class D audio amplifiers, the reduced electromagnetic interference (EMI) emissions allow for fast time-to-market without compromises in audio performance or efficiency. In mains‑powered multi-channel applications, the reduced and scalable EMI enables otherwise impossible industrial designs without needing a heatsink or a traditional LC filter.

A high-order internal feedback loop ensures low total harmonic distortion (THD) and low noise floor for excellent audio performance. The inductor‑less application contributes to the smallest output filtering, avoiding bulky inductors, thus reducing system cost without output power limitations. The integrated DSP in the MA2304DNS is highly configurable and can correct imperfections and tune real speaker applications with, e.g., equalisation, limiting, and other similar functions. The MA2304PNS offers a simpler volume control and limiter for systems where an application/connectivity processor does the audio processing.

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