EVAL-ADAU1401EB AD [Analog Devices], EVAL-ADAU1401EB Datasheet - Page 20

• Manufacturer Part Number: EVAL-ADAU1401EB
• Description: SigmaDSP 28-/56-Bit Audio Processor with Two ADCs and Four DACs
• Manufacturer: AD [Analog Devices]

ADAU1401
AUDIO DACs
The ADAU1401 includes four Σ-Δ DACs. The SNR of the DAC
is 104 dB, and the THD + N is −90 dB. A full-scale output on
the DACs is 0.9 V
The DACs are in an inverting configuration. If a signal inversion
from input to output is undesirable, it can be reversed either by
using an inverting configuration for the output filter or by simply
inverting the signal in the SigmaDSP program flow.
The DAC outputs can be filtered with either an active or a
passive reconstruction filter. A single-pole, passive, low-pass
filter with a 50 kHz corner frequency, as shown in Figure 18, is
sufficient to filter the DAC out-of-band noise, although an
active filter may provide better audio performance.
rms
(2.5 V p-p).
DAC_OUT
4.75kΩ
4.75kΩ
150pF
Figure 19
Figure 19. Active DAC Output Filter
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470µF
AD8606
C8
47µF
shows a triple-pole, active, low-pass filter that provides a steeper
roll-off and better stop-band attenuation than the passive filter.
In this configuration, the V+ and V− pins of the AD8606 op
amp are set to VDD and ground, respectively.
To properly initialize the DACs, Bits DS [1:0] in the DAC setup
register (Address 2087) should be set to 01.
604Ω
3.3nF
DAC_OUT
Figure 18. Passive DAC Output Filter
49.9kΩ
47µF
FILTER_OUT
560Ω
5.6nF
FILTER_OUT