A new generation of high-performance audio ICs are solving the challenges of implementing audio functionality and sound quality into next-generation mobile devices. These ICs support a broad range of productivity and personal entertainment uses while reining in power consumption to maintain long battery life.
For designers, audio IC selection requires effectively juggling performance, real estate, battery life, cost, and time to market. In the past, audio performance rested on codecs, audio analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) with sufficient signal-to-noise ratio, and best harmonic distortion combined with low power. System-on-chips (SoCs) integrated functions in one large chip, yet cost, functionality, and time to market suffered.
Even greater audio quality demands exist today. Audio components must process signals at higher frequencies, at ever-lower power, and with minimum losses. In mobile devices, space continues to shrink, while the number of inputs and outputs involve stereo and mono audio signal mixing and routing, internal and external microphones, recording, and playback across a variety of digital audio formats, as the workhorse components handle traditional voice, multimedia files, streaming audio, and ringtones.
Today, given the small process geometries of smartphone processors and the greater integration of processing capabilities and graphics, audio functions are moving toward integration in an audio SoC, or hub device. These highly integrated audio devices incorporate multiple inputs/outputs and functions, enabling designers to eliminate the need for additional components.
With audio externally implemented, chips with different process technologies are easily used, and moving audio functions from the main processor makes it possible to integrate a variety of functions into standalone amps and gain ease of design as well as improved audio performance and efficiency.
An example of the more modern integration approach is Qualcomm Technologies’ DDFA digital amplifier technology. Integrated into a single chip, the CSRA6640 allows audio OEMs to reduce external components, enabling commercially viable high-end Class-D amplification for compact and lower-tier devices.
The CSRA6640 offers clearer and louder audio than linear and analog amplifiers, and its integrated DSP and Class-D amplifier delivers up to 20 W per channel. The chip can also bridge output drivers to create a single 40-W amplifier. The chip responds to fluctuation in the speaker output to protect against failures, preserving low-noise, low-distortion, and high-dynamic-range audio. If you’re lacking specific amplifier experience, an evaluation kit combines the hardware, software, development tools, and information to easily integrate DDFA capabilities into products.
Several companies are plugging signal processing directly into amplifier ICs. Texas Instruments Inc., for example, recently introduced smart audio amplifiers for voice-controlled devices. Its TAS2770 delivers audio clarity and loudness yet only consumes 15 W. The amplifier IC employs unique audio-processing algorithms that deliver richer audio, echo cancelling, and protection against clipping that causes audio playback issues. A second audio IC, the TAS5825M , delivers dedicated serial audio interface information to the applications processor that supports echo cancellation and offers thermal protection via real-time accurate voltage and current sensing.
The use of Class-D audio amplifiers can achieve energy efficiencies above 90% by eliminating linear gain devices and other analog components. Cirrus Logic Inc. is also integrating DSPs into its Class-D devices. The Cirrus Logic CS35L41 smart power amplifier , according to the company, is 50% smaller than competitive ICs and combines an advanced power management system and advanced algorithms to adapt to changing audio, speaker, and battery conditions in portable devices without diminishing audio performance. The smart power amp increases the audio volume when in speaker-phone mode yet reduces noise and power consumption for improved battery life and talk times.