audio/videoZONE Products for the week of June 30, 2003
AKM Semiconductor Says . . .
AK4366/67: Low Power 24-bit DAC Integrating Headphone
Amplifier
Asahi Kasei Microsystems Co., Ltd. (AKM), a leading supplier of audio ICs for professional and consumer markets introduced the AK4366/67, very low power consumption, 24-bit 2-channel DAC with integrated high output headphone amplifier and ultra-small profile, which make them highly suitable for achieving ultra-compact memory players, cellular phones, and PDAs.
As a result of the progressive reductions in their size and in power consumption, memory players have rapidly become popular as basic players as well as a function to add to cellular phones and PDAs. Because of their ease of use and power efficiency, memory players are a preferred application for DAC capable of replaying audio signals.
Among AKM devices, the AK4366/67 is 35 percent smaller and consumes 50 percent less power even higher output of 50mW for headphone amplifier making it the smallest power consuming in AKM's lineup of DACs with a built-in headphone amplifier.
Besides the very small size and low power consumption advantages, the AK4367 supports analog mixing functions enabling the side tone, beep and other analog signals in equipments such as cellular phones to be mixed with the headphone amplifier output, and incorporates a mono line output that allows the stereo output to be mixed, which makes possible control of the volume of sound sent to an external speaker amplifier independently of the stereo output.
The AK4366, a single-function DAC without the mixing functions and mono
line output of the AK4367, is ideal for audio players. Both devices incorporate
an amplifier mute circuit; bass boost circuit and de-emphasis circuit, and
digital volume controls.
analogZONE Says...
This is a novel product: A dual channel 24-bit audio DAC with on-chip headphone amplifiers to directly drive up to 50-mW per channel into 16 ohms (3.3 V rail.) It is equipped with a bass boost filter which provides 5.76 dB, 10.80 dB, or 16.06 dB boost at 20 Hz. This allows for the coupling capacitor in each output line to be smaller than it otherwise might be because it and the filter formed with the resistive load determine the low frequency response of the signal to the headphones.
The bass boost is followed by a digital filter with a 0.05dB passband from 0 Hz to 20 kHz. The output of the DACs feed the headphone amplifiers (in the AK4366) and mute circuits are provided on the outputs. In the AK4367 a mixing circuit is provided before the headphone amplifiers for cross-channel mixing and the addition of external signals. This also provides a mixed "mono" output with separate gain attenuation up to 30 dB in 2-dB steps.
All the THD and SNR numbers are way more than adequate for extremely high-quality headphone listening with plenty of power. Sampling rates can be chosen from 8 kHz to 48 kHz with 64x oversampling. The input format can be MSB First, 2s complement-I2S, 24-bit MSB justified, and 24-bit/20-bit/16-bit LSB justified at CMOS levels. The rail voltage can be between 2.2 V and 3.6 V with a 2.6 mA draw typical for the AK4366 and 2.8 mA for the AK4367. Shutdown is a typical 1 µA.
This is a neat part that should easily find sockets in portable products where the OEM is not desperate to eliminate output coupling capacitors. The bass boost covers up a lot of the problems of using smaller output coupling capacitors and in most applications the user will be unaware the boost is there. The premium for adding the mixing facilities in the AK4367 seems a little high at first glance, but if you want these facilities you would otherwise pay rather more.
Both the AK4366 and AK4367 are sampling with the AK4366 in a TSSOP-16 priced at $2.89, and the AK4367 in a QFN-20 priced at $4.61, both in 1000-piece lots.
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