DSM smart amplifier unleashes micro speaker potential

The boosted, digital Class D DSM smart amplifier unleashes a system’s full audio potential by safely driving higher power levels (up to 5.1W) into tiny speakers typically rated for much lower power between one to three watts.

The miniaturisation of consumer devices requires speakers to fit within smaller form factors, which has led to more applications moving towards the use of micro speakers. As speakers shrink, loudness or sound pressure level (SPL) decreases while the resonant frequency increases, leading to less bass. Driving the speakers harder to increase loudness and bass response can easily damage the micro speakers through overheating and over excursion. 

MAX98390 solves this challenge by utilising integrated IV (current and voltage) sense and Maxim’s DSM algorithm to drive speakers to their maximum specified limits, while protecting against over excursion and over-temperature events. 

DSM’s thermal protection empowers designers to safely push their speakers well beyond their specified power rating enabling the speakers to produce their maximum loudness. DSM’s excursion protection enables designers to drive speakers to their specified excursion limits, producing sound up to two octaves below the resonant frequency limit.

To properly protect the speaker, amplifier algorithms must know the characteristics of the speaker, such as resonant frequency within its enclosure, excursion limit and voice coil thermal limit. Traditionally, designers had to go through the time-consuming and complex characterisation process or rely on direct supplier support to characterise their speakers and enclosures. 

This challenge is further exacerbated as most projects start prototyping with multiple speakers per project, requiring several weeks of supplier support or requiring special equipment and expertise. The MAX98390 significantly reduces the design time through the easy-to-use DSM Sound Studio GUI that allows customers to quickly and easily characterise many speakers. 

Combined with DSM’s thermal protection, the result is maximum loudness across the significantly extended frequency ranges in minutes, with no complex programming required. To cater to the miniaturisation of devices and shrinking batteries, the MAX98390 offers industry-leading peak efficiency at 86 percent, which is even further improved with DSM’s Perceptual Power Reduction (PPR) feature that can yield up to an additional 25 percent efficiency, and the lowest quiescent power consumption of ~24mW, making it the ideal choice for low power devices that need longer battery life.

Advantages

• Louder and deeper sound quality: Delivers up to 2.5x loudness (Sound Pressure Level) and up to two octaves deeper bass versus conventional 5V amplifiers in a small form factor.
• Ease of use: Includes Maxim’s brand-new DSM Sound Studio software GUI, which enables designers to clearly hear the DSM difference in minutes with the Quick Demo feature, and easily characterise and prototype with their own speakers, significantly reducing design time and work.
• Low power consumption: Features low quiescent power with ~24mW; offers peak efficiency of 86% with boosted Class D Amplifier; and further improves efficiency by up to 25 percent with no loss in audio fidelity with Maxim’s DSM PPR feature.
• Designed for manufacturability: On-chip DC resistance (Rdc) testing can be used on the production line for quality assurance to ensure speaker is within impedance tolerance.

The MAX98390 is available at Maxim’s website for $1.95; also available from authorised distributors.