AK4524 Datasheet, PDF (28/31 Pages) Asahi Kasei Microsystems – 24BIT 96KHZ AUDIO CODEC

ASAHI KASEI
[AK4524]
3. Analog Inputs
The IPGA inputs are single-ended and the input resistance 5kW (min). The input signal range scales with the VREF voltage
and nominally 0.58 x VREF Vpp centerd in the internal common voltage (about VA/2). Usually the input signal is AC
coupled with capacitor. The cut-off frequency is fc=(1/2pRC). The AK4524 can accept input voltages from AGND to VA.
The ADC output data format is 2’s complement. The output code is 7FFFFFH(@24bit) for input above a positive full scale
and 800000H(@24bit) for input below a negative fill scale. The ideal code is 000000H(@24bit) with no input signal. The
DC offset including ADC own DC offset removed by the internal HPF.
The AK4524 samples the analog inputs at 64fs. The digital filter rejects noise above the stopband except for multiples of
64fs. The AK4524 includes an anti-aliasing filter (RC filter) to attenuate a noise around 64fs.
4. Analog Outputs
The analog outputs are full differential outputs and nominally 0.54 x VREF Vpp centered in the internal common voltage
(about VA/2). The differential outputs are summed externally, Vout=(AOUT+)-(AOUT-) between AOUT+ and AOUT-.
If the summing gain is 1, the output range is 5.4Vpp (typ@VREF=5V). The bias voltage of the external summing circuit is
supplied externally. The 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 AOUT is 0V for 000000H(@24bit).
The internal switched-capacitor filter and the external LPF attenuate the noise generated by the delta-sigma modulator
beyond the audio passband.
Differential outputs can eliminate any DC offset on analog outputs without using capacitors. Figure 12 to Figure 14 show
the example of external op-amp circuit summing the differential outputs.
AOUT-
4.7k
4.7k
R1
470p
3300p
Vop
AOUT+
4.7k
Vop
4.7k
R1
-
+
470p
Analog
Out
1k
BIAS 0.1u
47u ⁺
1k
When R1=200ohm
fc=93.2kHz, Q=0.712, g=-0.1dB at 40kHz
When R1=180ohm
fc=98.2kHz, Q=0.681, g=-0.2dB at 40kHz
Figure 12. External 2nd order LPF Example (using single supply op-amp)
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