ASAHI KASEI
[AK4309B]
1. Grounding and Power Supply Decoupling
To minimize coupling by digital noise, decoupling capacitors should be connected to AVDD and DVDD,
respectively. AVDD is supplied from analog supply in system and DVDD is supplied from AVDD via 10Ω
resistor as shown in Figure 3 . Alternatively if AVDD and DVDD are supplied separately, AVDD and DVDD
should be powered at the same time or AVDD should be powered earlier than DVDD. Analog ground and
digital ground should be connected together near to where the supplies are brought onto the printed circuit
board. Decoupling capacitors for high frequency should be placed as near as possible.
2. Voltage reference
The differential Voltage between VREFH and VREFL set the analog output range. VREFH pin is normally
connected to AVDD and VREFL pin is connected to AVSS with a 0.1uF ceramic capacitor. VCOM is a signal
ground of this chip. An electrolytic capacitor of around 10uF in parallel with a 0.1uF 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 clocks, should be kept away from the VREF and VCOM pins in order to avoid unwanted
coupling into the AK4309B.
3. Analog Outputs
The analog outputs are also single-ended and centered around the VCOM voltage.The output signal range is
typically 3.4Vpp. AC coupling capacitors of larger than 1uF are recommended.The internal switched-capacitor
filter and continuous-time filter attenuate the noise generated by the delta-sigma modulator beyond the audio
passband.Therefore, any external filters are not required for typical application. The output voltage is a
positive full scale for 7FFFH(@16bit) and a negative full scale for 8000H(@16bit). The ideal output is VCOM
voltage for 0000H(@16bit).
DC offsets on analog outputs are eliminated by AC coupling since analog outputs have DC offsets of VCOM +
a few mV.
0177-E-00
1997/6
- 11 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
