Small low-power boosted smart audio amplifier

By tackling the complex engineering challenges inherent in mobile stereo audio design, Cirrus Logic enables OEMs of smartphone and battery-powered portable devices to introduce a markedly improved audio listening experience for both mono and stereo applications, while conserving battery life.

The Cirrus Logic CS35L41 11-volt boosted Class D audio amplifier with DSP, complemented with Cirrus Logic’s SoundClear Playback software, improves audio quality and increases the loudness of smartphone speaker output while protecting the speaker using both hardware and software techniques. Its advanced battery management system and predictive algorithms adapt to changing audio, speaker and battery conditions to minimise power consumption and battery current, without sacrificing audio performance.

This new smart power amplifier also uses 55nm process technology, the most advanced for this class of amplifiers, resulting in a tiny, 5.64mm2 space-saving WLCS package. This is important to OEMs who want to include a two-speaker design, as well as pack in as many new features and functions as possible.

According to a SAR Audio Signal Chain IC forecast database from Q4 2018, market shipments for audio amplifiers have grown three times from 2010 to 2018 due to the increasing shipments of audio playing devices, and also the increasing number of channels per device.

SAR Insight Principal Analyst, Peter Cooney, stated: “Amplifier shipment growth in the smart phone market is due not only to an increase in stereo sound in high-end phones but also the mid-tier market, defined as phones priced between $200 and $500. We anticipate this growth to continue with an estimated increase from the 500 million amplifiers shipped into mid-tier phones in 2017, to almost 700 million by 2022.”

“More and more consumers are turning to their smartphone as a primary device for video streaming, gaming and listening to music – including using speakerphone or loudspeaker mode,” said Carl Alberty, Vice President of Marketing, Cirrus Logic. “The sound quality from a phone using the CS35L41 is so impressive that you can leave your portable speaker behind and simply carry one device to enjoy media anywhere you go without compromise.”

The Cirrus Logic CS35L41 boosted amplifier delivers on the ‘big three’ requirements for mobile applications: enriched audio sound, efficient low-power management and a space-saving package. By incorporating features such as advanced battery management and predictive algorithms, the Cirrus Logic smart power amp increases the audio volume when in speakerphone mode, while reducing noise and power consumption, resulting in better battery life and improved talk times.

The Cirrus Logic CS35L41 11-volt smart boosted Class D audio amplifier with DSP delivers high-performance audio in a small, low-power package. Design features include:

• Amplifier performance: The core of the Cirrus Logic CS35L41 features a 5.3-watt digital input, mono Class D amplifier with the lowest noise and idle power consumption in its class. An integrated 11-volt Class H DC-DC converter boosts the supply voltage and maintains higher efficiency than other audio power amplifiers relying on Class G boost regulators. By adaptively tracking the audio level, the Class H boost converter helps improve system efficiency, minimises power dissipation and preserves battery life.
• Audio enhancement: Cirrus Logic’s SoundClear Playback software provides the ability to fine tune audio to the specific micro speaker being used in the mobile system. Equalisation, compression and psychoacoustic enhancement algorithms improve sound clarity and increase loudness. Playback filtering compensates for the unique frequency response of the speaker, while eliminating pre-ringing found in conventional linear phase filters. This enables audio engineers to get the most out of small speakers and improve the gaming and video streaming audio experience for mobile device users.
• Battery management: The Cirrus Logic CS35L41 preserves battery life using an advanced battery management system, in addition to its Class H boost and super low 6.7-milliwatt (mW) quiescent current. By predictively managing the demand on the battery, the amplifier is able to maintain maximum loudness and audio quality, while protecting the battery by minimising battery current draw and eliminating unexpected ‘brown out’ conditions that shut down the phone.

The Cirrus Logic CS35L41 smart power amplifier is currently shipping in production volumes. The company also offers tuning tools that help enable not only top-tier smartphone and portable device OEMs to introduce higher quality mono and stereo audio, but mid- and lower cost designs as well.