[AK4344]
1. Grounding and Power Supply Decoupling
The AK4344 requires careful attention for power supply and grounding arrangements. VDD is usually supplied from the
analog supply in the system. 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 AK4344 as possible,
with the small value ceramic capacitor being the closest.
2. Voltage Reference
The differential Voltage between VDD and VSS sets the analog output range. VCOM is used as a common voltage of the
analog signal. VCOM pin is a signal ground of this chip. An electrolytic capacitor about 4.7μF should be attached
between VCOM pin and VSS. No load current may be drawn from VCOM pin. Especially, the ceramic capacitor should
be connected to this pin as near as possible.
3. Analog Outputs
The analog outputs are single-ended and centered around the VCOM voltage (0.5 × VDD). The output signal range is
typically 2.8Vpp (typ@VDD=3.3V). The internal switched-capacitor filter and continuous-time filter attenuate the noise
generated by the delta-sigma modulator beyond the audio passband. 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 (0.5 × VDD) for
000000H (@24bit).
DC offsets on analog outputs are eliminated by AC coupling since analog outputs have DC offsets of VCOM + a few mV.
Figure 21 shows an example of the external LPF with 2.8Vpp (1Vrms) output.
AK4344
10u
220
Analog
Out
LOUT / ROUT
2.8Vpp (1Vrms)
1nF
22k
fc=723.4kHz, g=-0.013dB at 40kHz
Figure 21. External 1st order LPF Circuit Example
MS0641-E-00
2007/06
- 22 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
