FEATURE WEARABLES & IOT
Portable Audio: Unplugged and Wireless
Kenichi Kiyozaki, product manager at ON Semiconductor introduces a series of high-resolution audio processors, one of the company’s latest ultra-low power semiconductors devices, launched to support development of state-of-the-art earbuds - the latest advance in consumer trends
S
o many things are wireless these days, and those that are not, soon will be. One
of the simplest devices - headphones or earbuds - are still mostly tethered to the device via wires that can be frustrating, especially when they tangle. These wires often fail due to heavy use, or just simply from abuse! Recently, a major smartphone
manufacturer signalled a new era by dropping the headphone socket from its new product. This is only possible as wireless earbuds - a tiny pair of wireless speakers that fit inside the ear - are now able to offer the audio performance and functionality needed for music playback and streaming. Removing any physical socket helps sealing and makes smartphones and other portable/wearable devices much easier to waterproof. According to research firm
Marketsandmarkets, the wireless audio market is expected to reach USD54 billion by 2022. The change and growth in this market becomes much more apparent when coupled with the predicted CAGR of 23.2%. However, portable devices are very significant drivers in these predicted numbers and have become important entertainment devices in their own right. A more directly relevant study from Grand View Research cites technology advancements and miniaturisation as being key drivers that will lead the earbud and headphone market to exceed USD15 billion by 2024. Until now, wireless audio connectivity with
mobile devices has been limited to single-ear Bluetooth devices for hands-free calling while driving. However, technology is enabling more from the mobile audio experience, mostly driven by the high-end headphones with great audio quality and high-end features such as noise cancelling and enhanced bass. However, designing feature-rich, high
quality audio earbuds is a significant challenge. Efficiency and low power operation are crucial for ultra-small devices with extended operating times. Yet, desirable features such as deep bass and ambient noise cancelling cause a requirement conflict requiring a microphone and additional
14 MARCH 2017 | ELECTRONICS
development of state-of-the-art earbuds. Based on a dual core ARM Cortex-M3 processor and a proprietary 32-bit DSP core, the system-on-a-chip (SoC) incorporates 1656KB of SRAM, 256KB of ROM, a real- time clock and three eMMC/SD interfaces, and a total of six, 10 bit ADCs. A high-resolution audio engine based on the LPDSP32 DSP chip, capable of 32bit and 192KHz audio processing and featuring an MP3 encoder forms the heart of the system. Flexibility is built-in with decoders for MP3, WMA and AAC formats. The LC823450 consumes just 110
circuitry, adding complexity and bulk, thereby placing greater demands on the battery. A versatile and compelling earbud solution
will be expected to fulfill multiple functions including playback and streaming, as well as being used for voice calls and other tasks. With their small size and lack of tactile interface, wireless earbuds will almost certainly incorporate voice recognition. Semiconductors developed for earbuds
must allow designers to meet these conflicting demands, offering low power and high levels of integration alongside excellent audio processing performance plus a range of other features to support the desired functionality.
The LC823450 series of high-resolution
audio processors from ON Semiconductor is one of the latest ultra-low power semiconductor devices launched to support
Figure 1:
Overview of the LC823450 high- resolution audio processing system
microwatts for each Megahertz of operating speed allowing for audio playback times with two AAA batteries that are in excess of 120 hours – around 70% more than some other products on the market. The footprint of the XC and XD versions of
the device is just 5.52mm x 5.33mm - substantially less than other devices. DSP codes for noise cancellation and
variable speed playback that help designers accelerate software design and minimise development costs are just two items in a large selection of advanced royalty- and licensed-free DSP code libraries available from ON Semiconductor. Support devices add additional functionality
Figure 2:
An LC823450 audio system can use the BelaSigna chip to provide 'key phrase
for more complex systems. The 'always listening' BelaSigna R281 enables voice command response by detecting a single trigger phrase. To conserve power, the main LC823450 system sleeps and the R281 listens for a particular phrase. When detected, the R281 sends a wake-up interrupt and the main LC823450 system receives, decodes and actions the voice commands. The portable audio market is in a state of
rapid change and growth. The consumer desire is in place for high-performance in- the-ear devices and dedicated, application- specific device ecosystems with high levels of integration and low power consumption, such as the LC823450, will play a significant role in making these desires a reality.
ON Semiconductor
www.onsemi.com T: +1 (888)-743-7826
/ ELECTRONICS
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