AK4618 Datasheet, PDF (55/60 Pages) Asahi Kasei Microsystems – 192kHz 24-bit 6ch/12ch Audio CODEC with Microphone Interface

[AK4618]
1. Grounding and Power Supply Decoupling
The AK4618 requires careful attention to power supply and grounding arrangements. AVDD1, AVDD2 and TVDD are
usually supplied from analog supply in system. VSS1 ~ 3 of the AK4618 must be connected to analog ground plane.
System analog ground and digital ground should be wired separately and connected together as close as possible to where
the supplies are brought onto the printed circuit board. Decoupling capacitors should be as near to the AK4618 as
possible, with the small value ceramic capacitor being the nearest.
2. Voltage Reference
VCOM is a signal ground of this chip and output the voltage AVDD1x1/2. A ceramic capacitor 1µF attached to the
VCOM pin eliminates the effects of high frequency noise. This capacitor should be as close to the pin as possible. No load
current may be drawn from the VCOM pin. All signals, especially clocks, should be kept away from the VCOM pin in
order to avoid unwanted coupling into the AK4618.
3. Analog Inputs
The AK4618 supports single-ended and differential analog input. The single-ended input signal range scales with the
supply voltage and nominally 0.81xAVDD1 Vpp (typ). The differential input signal range between IN+ and IN scales
with the supply voltage and nominally ±0.81xAVDD1 Vpp (typ). The power supply voltage range of the AK4618 is from
VSS2 to AVDD1. The ADC output data format is 2’s complement. The internal HPF removes the DC offset.
The AK4618 samples the analog inputs at 64fs (@ fs=48kHz). The digital filter removes noise above the stop band except
for multiples of the sampling frequency of analog inputs. The AK4618 includes an anti-aliasing filter (RC filter) to
attenuate a noise around the sampling frequency of analog inputs.
4. Analog Outputs
The single-ended output signal range is nominally 0.86 x AVDD2 Vpp centered around the VCOM voltage. 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). The internal analog filters remove
most of the noise generated by the delta-sigma modulator of DAC beyond the audio passband, in single-ended input
mode. There are no internal analog filters for differential output mode, therefore this noise should be removed by the
external analog filters.
The DAC outputs have DC offsets of a few millivolts to VCOM voltage.
015000617-E-00
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2015/01