Datasheet
SLES102A – DECEMBER 2003 – REVISED NOVEMBER 2006
www.ti.com
18
APPLICATION INFORMATION
TYPICAL CONNECTION DIAGRAM
DATA
24
23
22
21
20
19
18
17
16
15
5
6
7
8
9
10
11
12
13
14
PCM1798
BCK
SCK
DGND
V
DD
MUTE
FMT0
FMT1
ZERO
RST
AGND2
I
OUT
R–
V
CC
1
V
COM
L
V
COM
R
I
REF
I
OUT
R+
AGND3R
AGND1
–
+
MONO
1
2
3
4
CHSL
DEM
LRCK
28
27
26
25
V
CC
2L
AGND3L
I
OUT
L–
I
OUT
L+
V
OUT
L-Channe
l
5 V
V
CC
2R
0.1 µF
Controller
10 µF
3.3 V
PCM
Audio
Data
Source
0.1 µF
10 µF
C
f
R
f
Differential
to
Single
Converter
With
Low-Pass
Filter
47 µF
5 V
10 µF
10 kΩ
–
+
C
f
R
f
–
+
V
OUT
R-Channe
l
C
f
R
f
Differential
to
Single
Converter
With
Low-Pass
Filter
–
+
C
f
R
f
0.1 µF
10 µF
5 V
+
+
+
+
+
Figure 23. Typical Application Circuit
APPLICATION CIRCUIT
The design of the application circuit is very important in order to actually realize the high S/N ratio of which the
PCM1798 is capable. This is because noise and distortion that are generated in an application circuit are not
negligible.
In the third-order LPF circuit of Figure 24, the output level is 2.1 V RMS, and 123 dB S/N is achieved.
I/V Section
The current of the PCM1798 on each of the output pins (I
OUT
L+, I
OUT
L–, I
OUT
R+, I
OUT
R–) is 4 mA p-p at 0 dB (full
scale). The voltage output level of the I/V converter (Vi) is given by following equation:
Vi = 4 mA p–p × R
f
(R
f
: feedback resistance of I/V converter)
An NE5534 operational amplifier is recommended for the I/V circuit to obtain the specified performance. Dynamic
performance such as the gain bandwidth, settling time, and slew rate of the operational amplifier affects the audio
dynamic performance of the I/V section.
Differential Section
The PCM1798 voltage outputs are followed by differential amplifier stages, which sum the differential signals for each
channel, creating a single-ended I/V op-amp output. In addition, the differential amplifiers provide a low-pass filter
function.
The operational amplifier recommended for the differential circuit is the low-noise type.