SSM2135P データシートの表示（PDF） - Analog Devices
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SSM2135P Datasheet PDF : 12 Pages
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SSM2135
A Digital Volume Control Circuit
Working in conjunction with the AD7528/PM7528 dual 8-bit
D/A converter, the SSM2135 makes for an efficient audio
attenuator, as shown in Figure 37. The circuit works off a single
+5 V supply. The DAC’s are biased to a 2 V reference level
which is sufficient to keep the DAC’s internal R-2R ladder
switches operating properly. This voltage is also the optimal
midpoint of the SSM2135’s common-mode and output swing
range. With the circuit as shown, the maximum input and
output swing is 1.25 V rms. Total harmonic distortion measures
a respectable 0.01% at 1 kHz and 0.1% at 20 kHz. The fre-
quency response at any attenuation level is flat to 20 kHz.
Each DAC can be controlled independently via the 8-bit parallel
data bus. The attenuation level is linearly controlled by the
binary weighting of the digital data input. Total attenuation
ranges from 0 dB to 48 dB.
AD/PM-7528
L AUDIO
IN
4
47µF
REF A
FB
OUTA
DAC A
3
+5V
10µF+0.1µF
22
8
1
47µF
L AUDIO
3
1/2
OUT
4 SSM2135
DATA IN
6 DACA/
CONTROL
15 DACB
19
SIGNAL
CS
16
WR
R AUDIO
IN
18
47µF
REF B
FB
OUTB
20
DAC B
1
VDD
DGND
17 0.1µF 5
2.0V
+5V
1µF
1/2
6 SSM2135 47µF
7
R AUDIO
5
OUT
2kΩ
0.1µF +5V
+5V
100Ω
8
1
4
2
3 2.0V
7.5kΩ
1/2
5kΩ
SSM2135
A Logarithmic Volume Control Circuit
Figure 38 shows a logarithmic version of the volume control
function. Similar biasing is used. With an 8-bit bus, the
AD7111 provides an 88.5 dB attenuation range. Each bit
resolves a 0.375 dB attenuation. Refer to AD7111 data sheet for
attenuation levels for each input code.
L AUDIO
IN
R AUDIO
IN
DATA IN &
CONTROL
+5V
0.1µF
3
14 16
47µF
15
DGND
VIN
VDD
FB 1
OUTA
10
AD7111
AGND
2
+5V
0.1µF
3
14 16
47µF
15
DGND
VIN
VDD
FB 1
OUTA
10
AD7111
AGND
2
10
2.0V
1µF
+5V
10µF+0.1µF
28
1
3
1/2
4 SSM2135
47µF
L AUDIO
OUT
1/2
6 SSM2135 47µF
7
R AUDIO
5
OUT
2kΩ
0.1µF
100Ω
+5V
8
2
1
3
4
1/2
SSM2135
+5V
7.5kΩ
5kΩ
Figure 38. Single Supply Logarithmic Volume Control
Figure 37. Digital Volume Control
–10–
REV. D
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