AKD4528_05 Datasheet, PDF (2/45 Pages) Asahi Kasei Microsystems – 24Bit A/D & D/A converter

ASAHI KASEI
[AKD4528]
1. Analog Input Buffer Circuit
The ADC inputs are full differential and the input resistance is 27kΩ (typ. @fs=44.1kHz). The input signal range scales
with the VREF voltage and nominally 0.56 x VREF Vpp. It is recommended that the input DC bias voltage is 2.9V(The
bias is a voltage divided by resistors (3.3k and 4.7k) from VA in figure 2. The ADC output data format is 2’s complement.
The DC offset including ADC own DC offset removed by the internal HPF (fc=0.9Hz@fs=44.1kHz).
The AK4528 samples the analog inputs at 64fs. The digital filter rejects noise above the stopband except for multiples of
64fs. A simple RC filter may be used to attenuate any noise around 64fs though most audio signals do not have significant
energy at 64fs. Figure 2 is an example of differential input circuit.
2.8Vpp
4.7k
AK4528
1.5nF ³³⁰
AINR+ 2
-
+
330 NJM5532
AINR- 3
AINL+ 4
2.8Vpp
AINL- 5
Same circuit
5.96Vpp
4.7k
Vop+
4.7k
-
+
10k 22u
Signal
VA
Vop-
Vop+/-=+/-15V
3.3k
0.1u
VA=5V
BIAS
4.7k
+
10u
Input RC filter response : fc = 160kHz, g = -0.07dB at 20kHz, -0.26dB at 40kHz.
Figure 2. Differential Input Buffer Example
2.Analog Output Buffer Circuit
The 2nd-order LPF (fc=93.2kHz, Q=0.712) which adds differential output of AK4528 is implemented on the board.
When the further attenuation of the out-band noise is needed, some additional LPF is required. NJM5532D is used for
op-amp. Analog signal is output through BNC connectors (AOUTL, AOUTR) on board, and the output level of AK4528
is about 5.4Vp-p.
AOUT-
4.7k
4.7k
200
470p
AOUT+
3300p
4.7k
4.7k
+Vop
200
-
+
470p -Vop
Analog
Out
fc=93.2kHz, Q=0.712, g=-0.1dB at 40kHz
Figure 3. External 2nd order LPF Example (using dual supply op-amp)
<KM063101>
-2-
2005/11