Datasheet

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SBAS342B − DECEMBER 2004 − REVISED APRIL 2006
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16
APPLICATIONS INFORMATION
A typical connection diagram for the PCM4201 is shown
in Figure 11. Power supply bypass and reference
decoupling capacitors are included, and are labeled with
recommended values. The 0.1µF capacitors should be
X7R ceramic chip type, although other low ESR capacitor
types may also be used. The 10µF capacitors may be low
ESR tantalum, multilayer ceramic, or aluminum
electrolytic capacitors. Analog and digital ground pins
should be connected at a common point, preferably
beneath the PCM4201 package.
Printed circuit board layout is critical for best performance.
Please refer to the PCM4201EVM User’s Guide (TI
literature number SBAU108) for an example of a design
and layout that meets the published specifications for the
PCM4201.
INPUT BUFFER CIRCUIT EXAMPLES
The PCM4201 analog input requires some type of input
buffer or signal conditioning circuitry, especially when
interfacing to a microphone capsule. The input buffer or
amplifier must incorporate at least a single pole, RC
low-pass filter in order to provide antialias filtering for the
delta-sigma modulator. A filter with a −3dB corner
frequency in the range of 100kHz to 150kHz should be
sufficient for common audio output sampling rates equal to
or greater than 44.1kHz. However, a low-pass filter with a
lower corner frequency and possibly a higher filter order
will be required when running at the lower sampling rates,
depending upon the system requirements. Examples of
single-ended and differential input circuits are shown in
Figure 12 and Figure 13, respectively.
V
IN
+
V
IN
−
AGND
V
CC
RATE
S/M
RST
HPFD
V
REF
+
V
REF
−
DGND
V
DD
SCKI
BCK
FSYNC
DATA
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
PCM4201
From
Control
Logic
DSP, FPGA,
or
DIT4096
System Clock
0.1
µ
F
+
10
µ
F
0.1
µ
F
+
10
µ
F
+1.8V to +3.6V
Analog
Input
Input
Buffer
10
µ
F0.1
µ
F
+5V
+
Figure 11. Typical Connections for the PCM4201