PCM1741/E2K BURR-BROWN [Burr-Brown Corporation], PCM1741/E2K Datasheet - Page 16

• Manufacturer Part Number: PCM1741/E2K
• Description: +3.3V Single-Supply, 24-Bit, 96kHz Sampling Enhanced Multilevel, Delta-Sigma, Audio DIGITAL-TO-ANALOG CONVERTER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

ZERO FLAGS
Zero Detect Condition
Zero Detection for each output channel is independent from
the other. If the data for a given channel remains at a “0”
level for 1024 sample periods (or LRCK clock periods), a
Zero Detect condition exists for that channel.
Zero Output Flags
Given that a Zero Detect condition exists for one or more
channels, the Zero Flag pins for those channels will be set to
a logic “1” state. There are Zero Flag pins for each channel:
ZEROL (pin 12) and ZEROR (pin 11). These pins can be used
to operate external mute circuits, or used as status indicators
for a microcontroller, audio signal processor, or other digitally
controlled functions.
The active polarity of Zero Flag output can be inverted by
setting the ZREV bit of Control Register 22 to “1”. The reset
default is active high output, or ZREV = 0.
The L-channel and R-channel common Zero Flag can be
selected by setting the AZRO bit of Control Register 22 to “1”.
The reset default is L-channel and R-channel independent
Zero Flag, or AZRO = 0.
APPLICATIONS INFORMATION
CONNECTION DIAGRAMS
A basic connection diagram is shown in Figure 11, with the
necessary power-supply bypassing and decoupling compo-
nents. Texas Instruments recommends using the component
values shown in Figure 11 for all designs.
The use of series resistors (22 to 100 ) are recommended
for the SCK, LRCK, BCK, and DATA inputs. The series
resistor combines with stray PCB and device input capaci-
tance to form a low-pass filter that reduces high-frequency
noise emissions and helps to dampen glitches and ringing
present on clock and data lines.
16
FIGURE 11. Basic Connection Diagram.
+3.3V
Regulator
+3.3V
Audio Data
PCM
Input
+
+
10 F
10 F
L-Chan OUT
Post LPF
1
2
3
4
5
6
7
8
BCK
DATA
LRCK
DGND
V
V
V
V
DD
CC
OUT
OUT
L
R
POWER SUPPLIES AND GROUNDING
The PCM1741 requires a +3.3V analog supply (V
+3.3V digital supply (V
power the DAC analog and output filter circuitry, while the
+3.3V (V
interface circuitry. For best performance, the +3.3V (V
supply should be derived from the +3.3V (V
linear regulator, as shown in Figure 11.
Proper power-supply bypassing is shown in Figure 10. The
10 F capacitors should be tantalum or aluminum electrolytic,
while the 0.1 F capacitors are ceramic (X7R type is recom-
mended for surface-mount applications).
DAC OUTPUT FILTER CIRCUITS
Delta-sigma DACs utilize noise-shaping techniques to im-
prove in-band Signal-to-Noise Ratio (SNR) performance at
the expense of generating increased out-of-band noise above
the Nyquist Frequency, or f
be low-pass filtered in order to provide the optimal converter
performance. This is accomplished by a combination of
on-chip and external low-pass filtering.
Figures 9(a) and 10 show the recommended external low-
pass active filter circuits for single- and dual-supply applica-
tions. These circuits are second-order Butterworth filters
FIGURE 10. Dual-Supply Filter Circuit.
ZEROR/ZEROA
V
IN
ZEROL/NA
AGND
V
SCK
DD
COM
MC
MD
ML
R
1
) supply is used to power the digital filter and serial
16
15
14
13
12
11
10
9
R-Chan OUT
Post LPF
R
C
2
2
R
3
DD
System Clock
10 F
). The +3.3V supply (V
Control
Zero Mute
S
Mode
Control
C
/2. The out-of-band noise must
2
3
1
OPA2134
1
CC
) supply using a
PCM1741
R
CC
4
SBAS175
) is used to
CC
A
V
) and a
–
V
OUT
R
R
DD
2
1
)