Datasheet
®
9 PCM1704
FIGURE 4. Audio Interface Connections for Stereo Audio
Application.
FIGURE 5. Typical Application Circuit (one channel shown).
DOR
WCKO
BCKO
DOL
DATA
WCLK
BCLK
DATA
WCLK
BCLK
DF1704 or Other
Digital Filter PCM1704
PCM1704
24-Bit
96kHz
Data
TYPICAL APPLICATION
EXAMPLES
The audio interface connections for a stereo audio applica-
tion is shown in Figure 4. The audio data is input to the
digital filter, which then oversampleS the data by a factor of
8. The audio data is then filtered digitally and output to the
PCM1704 DACs.
Figure 5 shows single channel circuit connections for a
typical PCM1704 application. It shows the PCM1704 inter-
face to the digital filter, the I/V converter, and the DAC post
filter. Selection of an appropriate op amp for the I/V con-
verter is critical for obtaining optimum dynamic perfor-
mance from the PCM1704. The OPA627 is recommended
for this application. Op amps with similar characteristics and
faster settling times may also be used.
The suggested DAC post filter is a second-order lowpass
active filter, using the multiple feedback (MFB) circuit
technique. The OPA2134 is an excellent choice for the op
amp in this circuit, since it is designed for high performance
audio applications. The post filter is used to reconstruct and
band limit the DAC output signal.
20
19
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
9
10
C
1
C
2
C
4
C
3
C
5
+
Digital
Controls
Aluminum
Electrolytics
–5V
100µF
0.1µF
+
C
7
+
+
+
4.7µF
OPA627
1/2
OPA2134
47pF
+
4.7µF
+
C
6
+
+
100µF
0.1µF
+
100µF
0.1µF
+
+5V
–15V
Audio
Output
+15V
100µF
0.1µF
+
PCM1704U
DATA
BCLK
NC
–V
DD
DGND
+V
DD
WCLK
NC
20BIT
INVERT
–V
CC
REF DC
NC
SERVO DC
AGND
AGND
I
OUT
NC
BPO DC
+V
CC
8X
Oversampling
Interpolation
Filter
2.5kΩ
U1
U2
4.7kΩ
4.7kΩ
2kΩ
4.7µF
560pF
2200pF
+
4.7µF
+
DAC I/V Post Filter
24-Bit
96kHz Data
C
1
= 4.7µF
C
2
= 4.7µF
C
3
= 4.7µF
C
4
= 47µF
C
5
= 47µF
C
6
= 100µF
C
7
= 4.7