PCM1741/E2K BURR-BROWN [Burr-Brown Corporation], PCM1741/E2K Datasheet - Page 18

• 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]

18
Separate power supplies are recommended for the digital
and analog sections of the board. This prevents the switching
noise present on the digital supply from contaminating the
analog power supply and degrading the dynamic perfor-
mance of the PCM1741. In cases where a common +3.3V
supply must be used for the analog and digital sections, an
inductance (RF choke, ferrite bead) should be placed be-
tween the analog and digital +3.3V supply connections to
avoid coupling of the digital switching noise into the analog
circuitry. Figure 13 shows the recommended approach for
single-supply applications.
FIGURE 13. Single-Supply PCB Layout.
FIGURE 14. 8-Level Delta-Sigma Modulator.
8f
S
+
DIGITAL SECTION
Z
–1
RF Choke or Ferrite Bead
V
DD
+
Z
–1
+3.3V
REG
V
DGND
DD
Power Supplies
PCM1741
ANALOG SECTION
V
AGND
AGND
CC
8-Level Quantizer
THEORY OF OPERATION
The delta-sigma section of the PCM1741 is based on an
8-level amplitude quantizer and a fourth-order noise shaper. This
section converts the oversampled input data to 8-level delta-sigma
format. A block diagram of the 8-level delta-sigma modulator is
shown in Figure 14. This 8-level delta-sigma modulator has the
advantage of stability and clock jitter sensitivity over the typical
one-bit (2-level) delta-sigma modulator. The combined
oversampling rate of the delta-sigma modulator and the interpo-
lation filter is 64f
+
+
+
+V
–
S
64f
–V
S
S
Z
–1
Circuits
Output
S
.
+
Common
Ground
Z
–1
PCM1741
SBAS175