AK4683_07 Datasheet, PDF (81/84 Pages) Asahi Kasei Microsystems – Asynchronous Multi-Channel Audio CODEC with DIR/T

[AK4683]
1. Grounding and Power Supply Decoupling
The AK4683 requires careful attention to power supply and grounding arrangements. AVDD1, AVDD2, DVDD, PVDD
and HVDD are usually supplied from analog supply in system. If AVDD1, AVDD2, DVDD, PVDD and HVDD are
supplied separately, the power up sequence is not critical. AVSS1, AVSS2, DVSS PVSS and HVSS of the AK4683
must be connected to 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 near to the
AK4683 as possible, with the small value ceramic capacitor being the nearest.
2. Voltage Reference Inputs
The voltage of AVDD1, AVDD2 sets the analog input/output range. VCOM is a signal ground of this chip. An
electrolytic capacitor 2.2μF parallel with a 0.1μF ceramic capacitor attached between VCOM pin and AVSS1 pin
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 AVDD1, AVDD2 and VCOM pins in order to avoid unwanted coupling into the
AK4683.
3. Analog Inputs
The AK4683 receives the analog input through the single-ended Pre-amp using external resistors. Adjust the input
level/gain at Pre-amp to match the input range 1.22 x AVDD1 Vpp (typ. fs=48kHz, Ri =47kohm, Rf = 24kohm). Each
input pins are biased internally. The ADC output data format is 2’s complement. The internal digital HPF removes the
DC offset.
The AK4683 samples the analog inputs at 64fs. The digital filter rejects noise above the stop band except for multiples
of 64fs. The AK4683 includes an anti-aliasing filter (RC filter) to attenuate a noise around 64fs.
4. Analog Outputs
The analog outputs are also single-ended and centered around the VCOM voltage. The input signal range scales with
the supply voltage and nominally 0.6 x AVDD2 Vpp. 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.
DC offsets on analog outputs are eliminated by AC coupling since DAC outputs have DC offsets of a few mV.
5. Attention to the PCB Wiring
LIN1-6 and RIN1-6 pins are the summing nodes of the Pre-Amp. Attention should be given to avoid coupling with
other signals on those nodes. This can be accomplished by making the wire length of the input resistors as short as
possible. The same theory also applies to the LOPIN/ROPIN pins and feedback resistors; keep the wire length to a
minimum. Unused input pins among LIN1-6 and RIN1-6 pins should be left open.
MS0427-E-02
- 81 -
2007/04