Datasheet
www.ti.com
APPLICATION INFORMATION
Connection Diagram
1
2
3
4
5
6
7
8
BCK
DATA
LRCK
DGND
V
DD
V
CC
V
OUT
L
V
OUT
R
16
15
14
13
12
11
10
9
SCK
ML
MC
MD
ZEROL/NA
ZEROR/ZEROA
V
COM
AGND
Post LPF
+3.3V
Regulator
Mode
Control
Zero Mute
Control
System Clock
PCM
Audio Data
Input
+5V V
CC
L−Chan OUT
10 F
10µF
+
+
10µF
+
Post LPF
R−Chan OUT
µ
Power Supplies and Grounding
DAC Output Filter Circuits
PCM1742
SBAS176A – DECEMBER 2000 – REVISED APRIL 2005
A basic connection diagram is shown in Figure 28 , with the necessary power-supply bypassing and decoupling
components. Texas Instruments recommends using the component values shown in Figure 28 for all designs.
Figure 28. Basic Connection Diagram
The use of series resistors (22 Ω to 100 Ω ) is recommended for the SCK, LRCK, BCK, and DATA inputs. The
series resistor combines with stray PCB and device input capacitance 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.
The PCM1742 requires a 5-V analog supply (V
CC
) and a 3.3-V digital supply (V
DD
). The 5-V supply is used to
power the DAC analog and output-filter circuitry, while the 3.3-V supply is used to power the digital filter and
serial interface circuitry. For best performance, the 3.3-V supply should be derived from the 5-V supply using a
linear regulator, as shown in Figure 28 . The REG1117-3.3 from Texas Instruments is an ideal choice for this
application.
Proper power-supply bypassing is shown in Figure 28 . The 10- µ F capacitors should be tantalum or aluminum
electrolytic.
Delta-sigma DACs use noise-shaping techniques to improve in-band signal-to-noise ratio (SNR) performance at
the expense of generating increased out-of-band noise above the Nyquist frequency, or f
S
/2. The out-of-band
noise must 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.
Figure 27 (a) and Figure 29 show the recommended external low-pass active filter circuits for single- and
dual-supply applications. These circuits are second-order Butterworth filters using a multiple feedback (MFB)
circuit arrangement that reduces sensitivity to passive component variations over frequency and temperature. For
more information regarding MFB active filter design, see FilterPro™ MFB and Sallen-Key Low-Pass Filter Design
Program (SBFA001 ), available from the TI Web site at http://www.ti.com.
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