PCM1808
www.ti.com
SLES177A–APRIL 2006–REVISED AUGUST 2006
APPLICATION INFORMATION
TYPICAL CIRCUIT CONNECTION DIAGRAM
Figure 26 is a typical circuit connection diagram. The antialiasing low-pass filters are integrated on the analog
inputs, VINL and VINR. If the performance of these filters is not adequate for an application, appropriate external
antialiasing filters are needed. A passive RC filter (100 Ω and 0.01 µF to 1 kΩ and 1000 pF) generally is used.
PCM1808
(5)
(1)
(1)
(3)
C
C
C
+
+
1
5
+
R-ch IN
L-ch IN
1
2
3
4
5
6
7
V
V
R
14
13
12
11
10
9
REF
IN
2
AGND
V L
IN
(2)
C
4
+
+
5 V
V
CC
V
DD
FMT
MD1
4 µs (min)
High/Low
Pin
Setting
3.3 V
(2)
C
3
DGND
SCKI
MD0
Mask
DOUT
BCK
(4)
X1
8
LRCK
PLL170x
DSP
or
Audio
Processor
S0113-02
(1) C1, C2: A 1-µF electrolytic capacitor gives 2.7 Hz (τ = 1 µF × 60 kΩ) cutoff frequency for the input HPF in normal
operation and requires a power-on settling time with a 60-ms time constant in the power-on initialization period.
(2) C3, C4: Bypass capacitors, 0.1-µF ceramic and 10-µF electrolytic, depending on layout and power supply
(3) C5: 0.1-µF ceramic and 10-µF electrolytic capacitors are recommended.
(4) X1: X1 masks the system clock input when using the clock-halt reset function with external control.
(5) Optional external antialiasing filter could be required, depending on the application.
Figure 26. Typical Circuit Connection Diagram
BOARD DESIGN AND LAYOUT CONSIDERATIONS
VCC, VDD PINS
The digital and analog power supply lines to the PCM1808 should be bypassed to the corresponding ground
pins with both 0.1-µF ceramic and 10-µF electrolytic capacitors as close to the pins as possible to maximize the
dynamic performance of the ADC.
AGND, DGND PINS
To maximize the dynamic performance of the PCM1808, the analog and digital grounds are not internally
connected. These grounds should have low impedance to avoid digital noise feedback into the analog ground.
They should be connected directly to each other under the PCM1808 package to reduce potential noise
problems.
VINL, VINR PINS
VINL and VINR are single-ended inputs. The antialias low-pass filters are integrated on these inputs to remove
the high-frequency noise outside the audio band. If the performance of these filters is not adequate for an
application, appropriate external antialiasing filters are required. A passive RC filter (100 Ω and 0.01 µF to 1 kΩ
and 1000 pF) is generally used.
19
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