Ultra-Low Power Intelligent System Wakeup ADC With Integrated AAA

• Asahi Kasei Microdevices’ A-D converter comes with integrated Acoustic Activity Analyzer (AAA) and audio buffer that is optimal for use in portable devices
• It has the ability to analyse sounds even during off-state, thus consuming low power

Asahi Kasei Microdevices Corporation (AKM) has developed the AK5706, a high-performance 24-bit stereo A-D converter (ADC) with integrated Acoustic Activity Analyzer (AAA), audio buffer and support for digital and high-SNR microphones. The product is ideal for applications such as smart speakers, wearable devices equipped with voice assistants and connected security devices that listen for specific sounds.

The AK5706’s AAA block continuously analyses incoming audio with respect to already specified criteria while the rest of the system remains powered off. This feature of the product helps in drastically reducing a product’s standby power consumption and thereby extends its battery life.

Within 7ms of detecting the qualified audio, the AK5706 wakes the system and begins recording to its internal buffer, capturing any audio events that may occur while the SoC is booting. Once fully awake, the system SoC reads the buffer contents to determine the action required to be taken.

Features

Ultra-low power consumption and diverse system wakeup options

The AK5706’s external trigger input allows it to wake the system based upon stimuli from sensors such as human presence detectors, door sensors, and motion detectors. Even greater power savings may be achieved by using the external trigger input and AAA together, such that the AK5706 waits for human presence (11μA) and only then starts listening for qualified audio (30μA).

Built-in audio buffer for storing pre-boot audio

The AK5706’s 64kB buffer can record up to two seconds of audio, depending upon the quality and channel count, capturing audio that occurred during SoC boot. Data stored in the buffer can be read at high speed via SPI, making it suitable for smart speakers and other assistant-enabled devices.

High-resolution audio capture with low power consumption

The AK5706 is a low-power, high-performance 24-bit stereo ADC with a dynamic range of 105dB (stereo 24-bit, 192kHz operation consumes 1.6mA). The ADC performance makes it ideal for wearables and other power-conscious mic-enabled products, as well as security devices that require high-quality far-field recording.

About AAA 

The AAA or Acoustic Activity Analyzer assists in performing analogue time and frequency-domain analysis to determine whether an audio content falls within the specified criteria. AKM’s ultra-low-power analogue technology enables the AAA to listen for relevant audio while consuming just 30μA.

The AAA’s Noise Level Detector constantly tracks the ambient noise level in order to reduce false positives that may otherwise occur in a noisy environment. If a sound is louder than the current noise floor (as per user-specified data), the AAA classifies the audio content as low or high-frequency and short or long-duration. 

Human speech is generally classified as low-frequency and long-duration, so a user may reject any sounds that fall outside that parameter. If the product designer wishes to wake the system on a door knock, they may look for low-frequency, short-duration sounds. Additionally, the AAA has a mode that exclusively detects T3 (smoke detector) and T4 (carbon monoxide detector) alarm sounds. 

Samples are available now. Mass production of the AK5706 is scheduled for the autumn of 2020.

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