Want your speakers to sound loud enough? This key technology is very important

In today's consumer electronics market, micro speakers have been widely used in a variety of devices, including gaming devices, smart home IoT devices, and wearable devices. Although those who turn up the volume of private electronic products in public places are often annoying, when buying, you will certainly prefer those with a wider loudness range while ensuring fidelity. How to improve the loudness and bass response of micro speakers has become the main design consideration for many audio designers.

Despite their small size, these micro speakers have the same basic components – diaphragms, voice coils and magnets – as traditional speakers. However, due to their smaller components and simpler construction, their overall form factor is more compact and thinner. However, the small size of micro speakers also brings some challenges. Their volume (sound pressure level) and bass response are usually limited because the smaller the speaker, the higher the resonant frequency, resulting in attenuated bass and weaker sound. However, by continuously monitoring and protecting the speaker from fault conditions, the speaker's volume and bass response can be significantly improved.

In micro speaker applications, the reliability challenges faced by devices have changed significantly compared to previous large-size speakers: the coil temperature of a micro speaker may be as high as 100 degrees Celsius in a closed mobile phone, and the vibration amplitude of the diaphragm may also reach the mechanical limit (if the limit is exceeded, the coil will collide with the magnetic circuit or the diaphragm will collide with the top plate protective cover).

Standard amplifiers cannot monitor and protect speakers from these two conditions, so the rated power of speakers is often set conservatively. The intelligent driver chip can calculate the impedance curve of the speaker by real-time monitoring of the voltage and current of the speaker drive signal, and further derive the resonant frequency, amplitude, and temperature rise of the speaker (or module), all of which will change dynamically due to different signals and changes in the environment.

This is where ADI’s patented Dynamic Speaker Management (DSM) technology can play a key role. DSM technology provides a safe way to drive micro speakers beyond their specified maximum power rating. The DSM algorithm can increase the volume (sound pressure level) by up to 2.5 times and extend the bass response up to two octaves below the resonant frequency while achieving excellent power efficiency.

Providing overshoot and overtemperature protection, the MAX98390 drives the speaker to its maximum limit

Today's consumer devices require speakers to fit into smaller spaces, resulting in more and more applications using micro speakers. The smaller the speaker, the lower the volume or sound pressure level (SPL), the higher the resonant frequency, resulting in bass attenuation. Increasing the volume and low-frequency response by driving the micro speaker harder can easily cause overheating and excessive diaphragm excursion, damaging the micro speaker.

The MAX98390 is a step-up digital DG class DSM smart amplifier that uses a 6.3mm2 package to safely drive micro speakers with typically lower rated power (up to about 3W) to higher power (up to 5.1W), fully unleashing the full audio potential of the system. At the same time, it can also be used with 5W speakers to further enhance the volume and bass effect.

By using integrated IV (current and voltage) sensing technology and ADI's proprietary DSM algorithm, the MAX98390 can drive the speaker to its maximum limit and provide overshoot and overtemperature protection to easily meet the above design challenges. The thermal protection function of the DSM device enables designers to drive the speaker safely and stably, breaking through the rated power limit and obtaining the maximum volume. DSM diaphragm protection enables designers to drive the speaker to the specified limit of its diaphragm, breaking through the lower limit of the resonant frequency, and improving the low-frequency response (two octaves).

In summary, the MAX98390 can bring several advantages to micro speakers: louder volume and heavy bass sound effects. Compared with traditional 5V amplifiers, the volume is increased by up to 2.5 times (sound pressure level), the low-frequency sound range is extended by 2 octaves, and the package size is small; ease of use, with ADI's new DSM Sound Studio software GUI, the system functions can be quickly demonstrated, so that designers can clearly hear the application effect of DSM in a few minutes, and easily perform characteristic analysis and prototype construction on their own speakers, significantly reducing design time and workload; industry-leading power consumption: providing the lowest quiescent power consumption in the current market, the peak efficiency of the boosted Class D amplifier is as high as 86%, and with ADI's patented perceived power reduction (PPR) algorithm, an additional 25% power can be further increased without losing audio fidelity. The minimum quiescent power consumption is only 24mW, which effectively extends battery life without reducing fidelity.

Quickly design smart amplifier solutions with DSM Sound Studio GUI

To effectively protect the speaker, the amplifier algorithm must be based on a good understanding of the speaker’s characteristics, such as resonant frequency, diaphragm excursion limits, and voice coil thermal protection. Traditionally, designers must go through a time-consuming and complex characterization process or rely on supplier support to characterize their speakers and enclosures. Since most projects use different speakers during the prototyping phase, supplier support can take up to several weeks or require special equipment and expertise, further increasing the design challenge.

But with ADI's DSM Sound Studio GUI, this process has never been easier and faster, and it takes less than 3 minutes to describe and customize the speaker protection algorithm. DSM Sound Studio is a GUI tool for speaker parameter extraction, tuning, and custom DSM settings in the MAX98390. In addition, another optional GUI, the MAX98390C/D evaluation software, can be used to change the amplifier configuration, such as boost voltage, current limit, etc.

DSM Sound Studio enables fast demonstration, ultra-fast loudspeaker characterization, tuning, and easy evaluation of different loudspeakers and different tunes. DSM Sound Studio V2 provides a better user experience by providing more detailed contextual help, optimized parameter extraction, and richer stereo capabilities to help complete simple self-guided design.

The MAX98390 helps customers quickly and easily analyze the characteristics of a variety of speakers through the easy-to-use "DSM Sound Studio GUI", greatly reducing design time. Combined with DSM's thermal protection function, maximum volume can be achieved over an ultra-wide frequency range in just a few minutes without complex programming .