AK4317 Datasheet, PDF (16/19 Pages) Asahi Kasei Microsystems – 18BIT SCF DAC WITH ATT & MIXER

ASAHI KASEI
1. Grounding and Power Supply Decoupling
[AK4317]
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 inFigure 9 . 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 VREF and AVSS set the analog output range. VREF pin is normally
connected to AVDD 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
AK4317.
3. Analog Outputs
The analog outputs are also single-ended and centered around the VCOM voltage. The output signal
range is typically 2.8Vpp. 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 1FFFFH(@18bit) and a negative full scale for
20000H(@18bit). The ideal output is VCOM voltage for 00000H(@18bit).
DC offsets on analog outputs are eliminated by AC coupling since analog outputs have DC offsets of
VCOM + a few mV.
0172-E-01
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1997/5