audio/videoZONE Products for the week of January 19, 2004
AKM Says . . .
AK4386: 24-bit Audio DAC with advanced noise reduction
Asahi Kasei Microsystems Co., Ltd. (AKM), a leading supplier of audio ICs for professional and consumer markets today introduced the AK4386 DAC. This 3-volt, 24-bit D/A converter supports sampling rates from 8KHz to 96KHz, and features advanced noise reduction at 8 kHz sample rates, making it suitable for Set-Top Boxes, digital televisions and portable AV devices.
With portable phones and digital still cameras delivering motion-picture functions and with the interchange of data with DTVs and video recorders by memory card becoming commonplace, there is a strong demand for enhanced audio playback performance in STB/DTV and portable AV devices.
The AK4386 96 kHz stereo D/A converter answers the demand with a 100dB signal-to-noise ratio when sampling at 48 kHz for high-quality audio. The new DAC's built-in high-performance digital filter reduces aliasing noise by more than 64dB and cuts high frequency noise significantly. With half-rate-mode response, the AK4386 maintains a constant noise level in the audible zone over sampling rates from8KHz to 96 kHz.
The AK4386 utilizes AKM's advanced multi-bit delta-sigma modulator and
the low jitter performance of AKM's switched-capacitor (SC) technology.
3 volt operation simplifies DSP and a pin-strap parallel control mode eliminates
the need for an external microcontroller.
analogZONE Says...
The AK4386 is a 24-bit DAC with some advanced filtering techniques that will allow it to be design-worthy in stereo audio applications where clock jitter is excessive, which is likely to occur in portable audio applications like MP3 players and advanced cameras with audio facilities. The filtering, switched capacitor (CTF) and continuous time (CTF), only slightly reduces the frequency response from the DAC's 8 X FIR digital filter (±0.05 dB to 20 kHz with fs = 44.1 kHz) to ±0.5 dB.
The part is a nominal 3.0 V one but can operate from 2.2 V to 3.6 V -- allowing for operation under discharging battery voltage conditions -- with an operating current of typically 6 mA at 44.1 kHz (current will increase a little at higher clock rates) and a power save mode drain of typically 1.5 mA. Full shutdown reduces the current drain to a typical 10 µA.
The master clock for this 24-bit serial input part can be 512, 768, 1024, or 1536 fs for half-speed (8 kHz to 24 kHz), 256, 384, 512, or 768 fs for normal speed (8 kHz to 48 kHz), or 128, 192, 256, or 384 fs for double speed (48 kHz to 96 kHz). with an input format that can be 24-bit MSB justified, 16/24-bit LSB justified, or I2S compatible. The sampling speed is selected by control on two pins, while audio interface format is selected on another two pins. An 8 X interpolator is used in each channel before the delta-sigma modulators used for conversion. A digital de-emphasis filter can be externally enabled or disabled for 44.1 kHz operation. A common-voltage output pin is also provided from the two single-ended output buffers. Dynamic range and SNR are typically 100 dB, while SINAD is a typical 86 dB.
We would expect to see the AK4386 as a shoe-in for many high-end portable audio devices and as AKM is always very price competitive we would expect to see it also win sockets in STBs and like equipment.
The AK4386 is sampling in TSSOP-16 and evaluation boards are available.
The data sheet is available on request to AKM.