[AK4372]
AVDD
AK4372
110k
LIN1 pin
HP-Amp
LIN1HL bit
100k
Note: If the path is OFF and the signal is input to the input pin, the input pin should be biased to a voltage equivalent to
VCOM voltage (= 0.475 x AVDD) externally.
Figure 51. External Bias Circuit Example for Line Input Pin
1. Grounding and Power Supply Decoupling
The AK4372 requires careful attention to power supply and grounding arrangements. AVDD is usually supplied from the
analog power supply in the system and DVDD is supplied from AVDD via a 10Ω resistor. Alternatively if AVDD and
DVDD are supplied separately, AVDD should be powered-up after DVDD rises up to 1.6V or more. When the AK4372
is powered-down, DVDD should be powered-down at the same time or later than AVDD. VSS1 and VSS2 must be
connected to the 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 close to the AK4372 as
possible, with the small value ceramic capacitors being the nearest.
2. Voltage Reference
The input voltage to AVDD sets the analog output range. Usually a 0.1μF ceramic capacitor is connected between AVDD
and VSS1. VCOM is a signal ground of this chip (0.475 x AVDD). The electrolytic capacitor around 2.2μF attached
between VCOM anVSS1 eliminates the effects of high frequency noise, too. No load current may be drawn from the
VCOM pin. All signals, especially clock, should be kept away from AVDD and VCOM in order to avoid unwanted
coupling into the AK4372.
3. Analog Outputs
The analog outputs are single-ended outputs, and 0.48 x AVDD Vpp(typ)@−3dBFS for headphone-amp, 0.61xAVDD
Vpp(typ) @0dBFS for LOUT/ROUT centered on the VCOM voltage. The input data format is 2’s compliment. The
output voltage is a positive full scale for 7FFFFFH(@24bit) and negative full scale for 800000H(@24bit). The ideal
output is VCOM voltage for 000000H(@24bit).
DC offsets on the analog outputs should be eliminated by AC coupling since the analog outputs have a DC offset equal to
VCOM plus a few mV.
MS0684-E-02
2008/12
- 60 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
