ak4556 AKM Semiconductor, Inc., ak4556 Datasheet - Page 20

• Manufacturer Part Number: ak4556
• Description: 3v 192khz 24bit ?? Codec
• Manufacturer: AKM Semiconductor, Inc.

ASAHI KASEI
[AK4556]
1. Grounding and Power Supply Decoupling
The AK4556 requires careful attention to power supply and grounding arrangements. VA pin is usually supplied from
analog supply in system and VD pin is supplied from VA pin via 5.1Ω. Alternatively if VA and VD pins are supplied
separately, the power up sequence is not critical. VSS pin of the AK4556 should be connected to analog ground plane.
System analog ground and digital ground should be connected together near to where the supplies are brought onto the
printed circuit board. Decoupling capacitors should be as near to the AK4556 as possible, with the small value ceramic
capacitor being the nearest.
2. Voltage Reference
The input to VA voltage sets the analog input/output range. A 0.1µF ceramic capacitor and a 10µF electrolytic capacitor
are connected to VA and VSS pins, normally. VCOM is a signal ground of this chip. A 2.2µF electrolytic capacitor in
parallel with a 0.1µF ceramic capacitor attached to these pins eliminates the effects of high frequency noise. No load
current may be drawn from VCOM pin. All signals, especially clock, should be kept away from the VA, VD and VCOM
pins in order to avoid unwanted coupling into the AK4556.
3. Analog Inputs
The ADC inputs are single-ended and internally biased to the common voltage (50%VA) with 8kΩ (typ, @fs=48kHz,
96kHz, 192kHz) resistance. The input signal range scales with the supply voltage and nominally 0.7xVA Vpp (typ). The
ADC output data format is 2’s complement. The internal HPF removes the DC offset.
The AK4556 samples the analog inputs at 128fs (@ fs=48kHz), 64fs (@fs=96kHz) or 32fs(@192kHz). The digital filter
rejects noise above the stop band except for multiples of the sampling frequency of analog inputs. The AK4556 includes
an anti-aliasing filter (RC filter) to attenuate a noise around the sampling frequency of analog inputs.
4. Analog Outputs
The analog outputs are also single-ended and centered around the VCOM voltage. The input signal range scales with the
supply voltage and nominally 0.7 x VA Vpp (typ). The DAC input data format is 2’s complement. The output voltage is
a positive full scale for 7FFFFFH(@24bit) and a negative full scale for 800000H(@24bit). The ideal output is VCOM
voltage for 000000H(@24bit). If the noise generated by the delta-sigma modulator beyond the audio band would be the
problem, the attenuation by external filter is required.
DC offsets on analog outputs are eliminated by AC coupling since DAC outputs have DC offsets of a few mV.
MS0559-E-00
2006/11
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