AKM Launches Low Power Solution for True Wireless Stereo (TWS) Development with ANC and Promotes Complete Solution Portfolio

September 18 2020, 18:10
Demand for True Wireless Stereo (TWS) products reflect the growing demand for multi-function, health care, and connected wearable solutions, all requiring smaller and longer battery life devices. Asahi Kasei Microdevices (AKM) has recently introduced the AKM AK4336ECB ultra low power audio codec, a 4-channel ADC and one channel DAC that supports active noise cancelling designs, complementing its complete portfolio of audio systems and sensors for TWS development.

With the audio industry now strongly focused on the development of true wireless products with Active Noise Cancelling (ANC), combined with ambient sound control and improved audio experiences, AKM is naturally positioned to be a contender in this type of development with its latest family of converters.

As AKM details, its latest audio ICs achieve industry-leading Active Noise Cancelling (ANC) performance, and Ambient Sound Control for listening to surrounding sounds while users are wearing true wireless earbuds, enabling a natural listening experience and eliminating discomfort from the occlusion effect during speech. AKM's original Auto Tuning Tool automatically derives the filter design that leads to the best possible ANC performance for each earbud form-factor and housing design.

For that specific development, AKM now offers the AK4336ECB and AK4332ECB conversion devices with integrated additional features. These ICs feature AKM's proprietary Velvet Sound high-quality audio technology, transporting the renowned "real live sound" and high-end audio experiences to the realm of true wireless devices.
Block diagram of the AKM AK4336ECB 4ch ADC/1ch DAC ultra low power audio codec with headphone amplifier, SRC, and DSP built-in.

The latest AKM AK4336ECB is an ultra low power audio codec with 4-channels of ADC and one channel DAC, with headphone amplifier, asynchronous sample rate converter (SRC) and DSP built-in. According to AKM, the integrated device is suitable for Active Noise Cancellation (ANC) and call processing in headphones since the built-in low latency ADC and DSP can achieve high suppression noise-cancelling performance over a wide bandwidth. Additionally, the 32-bit monaural portable audio DAC with built-in headphone amplifier, optimized for low-consumption devices, contributes to high-quality music playback. The device is housed in a compact and thin, 54-pin package, ideal for small earbuds.
Block diagram of the AKM AK4332ECB advanced 32-bit DAC with headphone amplifier, dedicated to True Wireless Earphones.

The AKM AK4332ECB is the audio solution from the company, mainly targeted for high-quality audio, offering an advanced 32-bit DAC with headphone amplifier, dedicated to true wireless earphones. The AK4332ECB is a monaural portable audio Velvet Sound DAC that is able to achieve both high sound quality and ultra-low power consumption and is housed in a compact and thin, 30-pin CSP package.

Naturally, all TWS designs require also voice detection features and seamless control with ultra-low power consumption. AKM offers its Acoustic Activity Analyzer (AAA), an acoustic analysis solution using AKM's own analog technology, enabling always-on voice detection with ultra-low power. The AAA listens for audio activity in a very low-power state while the rest of the device remains powered off, detects only voice and can pass the detection flag to the waiting SoC. By storing data recorded by the ADC in an internal buffer (up to 2s recording capacity), the AAA can reliably send voice signals for voice recognition to the edge processing SoC.

The device targeting that development is the AKM AK5706ECB, a high-performance 24-bit/192kHz stereo A/D converter with integrated Acoustic Activity Analyzer (AAA), audio buffer, and support for digital and high-SNR microphones. Once qualifying audio content is detected, the audio buffer begins recording and the rest of the AK5706ECB wakes up, in turn waking other devices in the system as needed. Designed for systems that must listen for specific types of audio activity while consuming very low power (as low as 30μA), the AK5706ECB is ideal for products such all speech recognition systems.

Next-up, together with conversion, signal processing and voice detection, any TWS design will also require sensors for head-tracking, posture detection, activation when removed from the case, etc. AKM offers accurate head-tracking by combining the azimuth angle information of a tri-axis magnetic sensor and the posture information of a six-axis IMU which consists of accelerometer and gyroscope sensors mounted on the earbuds. Currently, TWS users are also expecting audio settings customization features for the individual head-related transfer functions (HRTF) and acoustic augmented reality (AR) technology features.

AKM's ultra-compact tri-axis magnetic sensor, AK09918C, enables sound localization by accurately tracking the head, fixing the sound source at an arbitrary position regardless of the orientation of the face and the direction of movement. This 3-axis electronic compass IC is available in a very small size (0.76 mm × 0.76 mm x 0.5 mm) while maintaining the highest performance of the range. The package is a pin pitch 0.4 mm, 4-pin WL - CSP (power supply 2 pins, 2 pins for I²C communication).

The AK09940 is another high precision tri-axis magnetic sensor alternative that can be used for position-tracking applications. In cases when sufficient performance is not possible due to magnetic field noise, the AK09940 solves the problem by increasing magnetic position tracking accuracy. Designed for industrial and scientific applications, the AK09940 has a very low power consumption current and is therefore ideal for wearable devices with small batteries and augmented reality applications.

Both these sensors are helpful in implementing azimuth detection and smart self-navigation, essential for environmental awareness. AKM's ultra-compact tri-axis magnetic sensors can offer a comfortable and safe navigation system with direction of travel obtained in combination with a connected smartphone. Combined with an acceleration sensor these systems are always capable of detecting the direction in which the user is heading, making it possible to have smart navigation features with voice, even without a connected smartphone. AKM's own magnetic offset compensation technology also contributes to smart navigation.

Finally, no TWS design is complete without a charging case. For that specific system, AKM offers full "in and out" detection of the earbuds, together with opening and closing detection of the case. Offering improved design flexibility for the vital earbuds housing, AKM's tri-axis magnetic smart switch enables efficient detection for opening or closing of the charging case and in or out of TWS from the charging case. 

While these designs normally use multiple Hall sensors that are able to detect magnetic fields in one direction, the AKM AK09970D tri-axis magnetic smart switch can replace multiple Hall sensors allowing space saving design. This low power device is equipped with a magnetic event interrupt function that allows developers to adjust the switching points (operating threshold), so that the installation layout of sensors and magnets can be extended. 

The AK09970D is an ultra-compact 3D magnetic smart switch, allowing a significant reduction in system space, with its 1.35mm2, 6-pin WL-CSP package - an ultra-small size compared to the conventional 3.0mm2, 16-pin QFN package. The AK09970D offers a high sensitivity setting of 36mT on tri-axis, being able to measure a wide range of magnetic fields from microtesla to millitesla since it offers a measurement resolution of 1.1μT/LSB in high sensitivity mode. In addition, a wide range setting of 101mT can be achieved via the Z axis.
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