AK4589_1 Datasheet, PDF (73/76 Pages) Asahi Kasei Microsystems – 2/8-Channel Audio CODEC with DIR

ASAHI KASEI
[AK4589]
1. Grounding and Power Supply Decoupling
The AK4589 requires careful attention to power supply and grounding arrangements. AVDD, DVDD, PVDD and
TVDD are usually supplied from analog supply in system. Alternatively if AVDD, DVDD, PVDD and TVDD are
supplied separately, the power up sequence is not critical. AVSS, DVSS and PVSS of the AK4589 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 AK4589 as possible,
with the small value ceramic capacitor being the nearest.
2. Voltage Reference Inputs
The voltage of VREFH sets the analog input/output range. VREFH pin is normally connected to AVDD with a 0.1µF
ceramic capacitor. VCOM is a signal ground of this chip. An electrolytic capacitor 2.2µF parallel with a 0.1µF ceramic
capacitor attached to VCOM 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 VREFH and VCOM pins in order to avoid
unwanted coupling into the AK4589.
3. Analog Inputs
ADC inputs are single-ended and internally biased to VCOM. The input signal range scales with the supply voltage and
nominally 0.62 x VREFH Vpp (typ). The ADC output data format is 2’s complement. The DC offset is removed by the
internal HPF.
The AK4589 samples the analog inputs at 64fs. The digital filter rejects noise above the stop band except for multiples
of 64fs. The AK4589 includes an anti-aliasing filter (RC filter) to attenuate a noise around 64fs.
4. Analog Outputs
The analog outputs are differential output and centered around the VCOM voltage. The input signal range scales with
the supply voltage and nominally 0.54 x VREFH 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 (AVDD/2) on analog outputs are eliminated without using capacitor. However AC coupling in Figure 51.
External 2nd order LPF Circuit Example is recommended to achieve better performance.
MS0339-E-00
- 73 -
2004/09