CS4327 Datasheet, PDF (14/36 Pages) Cirrus Logic – Low Cost, 20-Bit, Stereo, Audio D/A Converter

CS4327
Grounding and Power Supply Decoupling
As with any high resolution converter, the CS4327
requires careful attention to power supply and
grounding arrangements to optimize performance.
Figure 1 shows the recommended power arrange-
ments with VA+ connected to a clean +5 volt sup-
ply. VD+ should be derived from VA+ through a
2 ohm resistor. VD+ should not be used to power
additional digital circuitry. All mode pins which re-
quire VD+ should be connected to pin 6 of the
CS4327. All mode pins which require DGND
should be connected to pin 5 of the CS4327. Pins 4
and 5, AGND and DGND, should be connected to-
gether at the CS4327. DGND for the CS4327
should not be confused with the ground for the dig-
ital section of the system. The CS4327 should be
positioned over the analog ground plane near the
digital / analog ground plane split. The analog and
digital ground planes must be connected elsewhere
in the system. The CS4327 evaluation board,
CDB4327, demonstrates this layout technique.
This technique minimizes digital noise and insures
proper power supply matching and sequencing.
Decoupling capacitors should be located as near to
the CS4327 as possible.
Performance Plots
The following collection of CS4327 measurement
plots were taken from the CDB4327 evaluation
board using the Audio Precision Dual Domain Sys-
tem One.
Figure 13 shows the frequency response at a
48 kHz sample rate. The response is flat to 20 kHz
±0.1 dB as specified.
Figure 14 shows THD+N versus signal amplitude
for a 1 kHz 20-bit dithered input signal. Notice that
the there is no increase in distortion as the signal
level decreases. This indicates very good low-level
linearity, one of the key benefits of delta-sigma
digital to analog conversion.
Figure 15 shows a 16k FFT of a 1 kHz full-scale in-
put signal. The signal has been filtered by a notch
filter within the System One to remove the funda-
mental component of the signal. This minimizes
the distortion created in the analyzer analog-to-dig-
ital converter. This technique is discussed by Audio
Precision in the 10th anniversary addition of AU-
DIO.TST.
Figure 16 shows a 16k FFT of a 1 kHz -20 dBFS in-
put signal. The signal has been filtered by a notch
filter within the System One to remove the funda-
mental component of the signal.
Figure 17 shows a 16k FFT of a 1 kHz -60 dBFS in-
put signal.
Figure 18 shows the fade-to-noise linearity. The in-
put signal is a dithered 20-bit 500 Hz sine wave
which fades from -60 to -120 dBFS. During the
fade, the output from the CS4327 is measured and
compared to the ideal level. Notice the very close
tracking of the output level to the ideal, even at low
level inputs. The gradual shift of the plot away
from zero at signals levels < -110 dB is caused by
the background noise starting to dominate the mea-
surement.
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DS190F1