Traditionally, electronics designers use analog amplifiers requiring a digital-to-analog converter (DAC) and line driver amplifier on the application processor. This adds overall die cost to the speaker output and affects the form factor of the overall solution size. With the rise of voice-activated consumer devices, designers must also meet today's increased demand for superior audio quality, while maintaining a simplified, low-power and efficient design.
The MAX98357 pulse-code modulation (PCM) and MAX98358 pulse-density modulation (PDM) plug-and-play speaker amplifiers reduce the overall solution size by taking advantage of Maxim's clever pin-out and by significantly reducing the number of required components compared to typical analog amplifier designs. Since most users control their volume digitally upstream, these features enable customers to take advantage of Maxim's cost-effective wafer-level packaging (WLP) without the need for expensive vertical interconnect access (VIAs).
For superior audio quality, they feature a digital input for noise immunity, along with highest jitter tolerance, which Maxim claims are at least 8dB better than comparable competitive solutions. They also offer excellent electromagnetic interference (EMI) performance and allow the use of longer traces to the speakers without added external filtering.
To simplify design, the plug-and-play functionality only requires users to connect a single power supply and feed the bit clock (BCLK) and left-right clock (LRCLK) of both the MAX98357 and MAX98358, without needing a master clock (MCLK). These amplifiers further simplify designs by auto-configuring for up to 35 different clocking configurations and 128 different digital audio formats. This automatic configuration eliminates complicated I2C programming as there is no longer a need to rewrite base code to configure a design just to add audio functionality. As more applications (such as smart speakers) start requiring multi-directional/channel audio, the need for amplifiers like the MAX98357 and MAX98358 that can be easily daisy-chained to support speaker arrays (up to 8 channels supported by time division multiplex or TDM) will continue to grow.
Detailed specifications illustrate the reasons why Maxim claims the highest efficiency for the new chips, with the highest dynamic range in its product category (103.5dB), best-in-class total harmonic distortion (THD) noise (0.013%), and excellent click-pop performance (-66dBV out of shutdown) via extensive click-pop reduction circuitry.
The cost-effective implementation uses WLP with no expensive PCB VIAs required, and only one external component (bypass capacitor) and one supply voltage needed for most applications, while existing solutions typically require at least two external components as well as internal VIAs and two supply voltages. Available in a tiny solution size (1.93mm2 WLP), the chips allow three gain levels with easy connection.
"In addition to highest Class D efficiency and the best audio quality in this amplifier segment, our clever pin-out allows customers to take advantage of the size and low cost of the WLP package, which has been a game changer for many of our customers," says Greg Mow, Business Manager for Mobile Audio Solutions at Maxim Integrated.
The MAX98357 is available for $0.87; MAX98358 is available for $0.87; Both are available at Maxim's website as well as select authorized distributors. MAX98357EVSYS#WLP and MAX98358EVSYS#WLP (TQFN also available) evaluation kits are available for $59.50