The portable audio market is demanding premium sound quality solutions responding to the growing availability of high-resolution audio content. Improvements in video recording resolution also have increased the demand for high-resolution sound recordings. Targeting those new premium audio applications, Asahi Kasei Microdevices Corporation (AKM) has developed the AK4962, an advanced audio CODEC with DSP. This single chip solution integrates sound quality techniques using AKMs high-end audio knowledge, in combination with audio recording techniques from digital still/video cameras and hands-free techniques for automotive applications.
The AK4962 is the new, higher performing version of the AK4961 DAC that has been adopted by many portable audio products and smartphones since it was launched in 2014. The AK4962 enhances the high quality sound technologies introduced in the AK4961 and now features digital active noise cancelling for portable devices.
Based on AKM’s Velvet Sound architecture that has been widely adopted by well-established high-end audio companies, the AK4962ECB is an SPI/ I2C (1MHz) and SLIMbus device that adds various sound processing for mobile applications such as dual Tx/Rx noise suppression, echo canceling and hands-free communication, reducing the load on the main processor while improving battery consumption.
The new AK4962 also provides ambient noise reduction for clear sound experiences even in a noisy environment with headphones that have built-in microphones. This feature implements advanced digital active noise cancelling which also supports the integrated low-noise and low-power consumption microphone amplifier (PCM Recorder Class) and microphone power supply, allowing for high quality realistic sound recordings using the internal DSP.
According to AKM, the AK4962 achieves -106 dB THD+N and 125dB SNR, top level performances in D/A converters with an integrated headphone amplifier (Class-G -106dB THD+N and 125dB S/N) for portable devices. The AK4962 has improved audio reproduction capabilities by achieving under -100dB THD+N in all audible bands. It also provides more detail thanks to AKM’s switched capacitor filter and OSR Doubler technologies that are integrated into the brand’s premium D/A converters for high-end audio products. In addition, four different 32-bit digital filters can be selected, according to the user audio and system preferences, supporting 5-band EQ, Dynamic Range Control, ALC and Wind Noise Reduction Filter.
The AK4962ECB also features two low-jitter PLLs, crystal oscillator, impedance detection function for jacks/headsets/buttons/headphones, and four asynchronous SRCs, all in a 125-pin CSP package.
AK4490EN and AK8157A dedicated clock generator
Also responding to the needs of high-quality and high-resolution portable digital audio applications, AKM’s new AK4490EN and its dedicated clock generator, AK8157A, are now available. The AK4490EN is a 32-bit premium D/A converter featuring the company’s Velvet Sound technology, improving on the previous AK4490EQ, launched in 2014. Downsizing the package and now supporting a 1.8 V digital interface in addition to the conventional 3.3 V digital interface, the AK4490 is ideal for portable applications, with support for high resolution sources as a digital input and up to 768 kHz PCM and 11.2 MHz DSD (Direct Stream Digital) data.
To help simplify the system clocking and sustain audio performance, the sampling rate clock source can be switched between 44.1 kHz and 48 kHz multiples by using the AK8157A as a clock interface. This solves the complex clock routing and sourcing issues found in today’s portable devices.
The AK4490EN is the first device with a QFN package (6mm) in AKM’s Verita series, drastically downsized from the AK4490EQ (9mm). Together with the AK8157A multi-clock generator, the solution allows for audio products generating low phase noise, necessary for maximum audio performance. The AK4490EN achieves -112 dB THD+N and the D/A conversion reduces sound quality degradation caused by noise shaping realizing a flat noise floor up to 200 kHz with AKM’s original switched capacitor filter and OSR Doubler technology, in combination with 32-bit processing and L/R symmetrical layout.
The new device also offers five different 32-bit digital filter types, including short delay sharp roll-off and short delay slow roll-off filters, sharp roll-off filter, slow roll-off filter to preserve the phase difference and a new even slower roll-off filter. They are selectable according to the user audio and system preferences.