AK4358_06 Datasheet, PDF (33/36 Pages) Asahi Kasei Microsystems – 192kHz 24-Bit 8ch DAC with DSD Input

ASAHI KASEI
[AK4358]
4. External Analog Filter
It is recommended by SACD format book (Scarlet Book) that the filter response at SACD playback is an analog low pass
filter with a cut-off frequency of maximum 50kHz and a slop of minimum 30dB/Oct. The AK4358 can achieve this filter
response by combination of the internal filter (Table 18) and an external filter (Figure 27).
Frequency
20kHz
50kHz
100kHz
Gain
-0.4dB
-2.8dB
-15.5dB
Table 18. Internal Filter Response at DSD mode
AOUT-
2.5Vpp
2.0k
2200p
2.0k
AOUT+
2.5Vpp
1.8k
3300p
1.8k
4.3k
4.3k
1.0k
1.0k
270p
270p
+Vop
-
+
-Vop
Analog
Out ^5.65Vpp
Figure 27. External 3rd order LPF Circuit Example
Frequency
Gain
20kHz
-0.05dB
50kHz
-0.51dB
100kHz
-16.8dB
DC gain = 1.07dB
Table 19. 3rd order LPF (Figure 27) Response
AOUT-
2.5Vpp
AOUT+
2.5Vpp
3.9k
3900p
3.9k
4.7k
4.7k
R1
470p
+Vop
R1
470p ^-Vop
Analog
Out _6.05Vpp
When R1=180Ω
fc=90.1kHz, Q=0.735, g=-0.04dB at 40kHz
When R1=150Ω
fc=99.0kHz, Q=0.680, g=-0.23dB at 40kHz
Figure 28. External 2^nd order LPF Circuit Example for PCM
MS0203-E-01
- 33 -
2006/02