SSM2163_15 Datasheet, PDF (13/16 Pages) Analog Devices – Digitally Controlled 8 3 2 Audio Mixer

SSM2163
Mixing Additional Channels
Some mixing applications require more than four inputs for
each stereo channel. To meet the requirements of these systems,
two or more SSM2163s can be paralleled to provide additional
channels. A typical circuit is shown in Figure 26, which combines
two SSM2163s to form a 16-input, 2-output mixer. An SSM2135
dual audio op amp sums the outputs of each of the SSM2163s.
With this system, any of the 16 inputs can be mixed into either
or both of the output channels.
The circuit of Figure 26 illustrates dc coupling of the inputs.
DC coupling is practical with dual supplies and ground-
referenced inputs, because the dc offsets associated with single-
supply operation are reduced. However, ac coupling could also
be used, and employing both ac- and dc-coupled signals in one
mixer is also possible. In addition, this circuit illustrates the
connections for ± 5 V power supplies. Note that the negative
supply, as well as the positive supply, should be bypassed to
ground.
V_IN1
5
V_IN1
+5V
4 10
+
10µF
V_DD V_CC
0.1µF
20k
+5V
Implementing a Software-Controlled Pan-Pot
Pan and fade effects are important attributes of modern multi-
media presentations and similar applications. One way to
achieve these effects is to apply the input signal to two input
OBSOLETE VIN2
V_IN3
V_IN4
V_IN5
V_IN6
V_IN7
V_IN8
DATA IN
CLOCK
CHIP SELECT
SYSTEM MUTE
V_IN1
22
V_IN2
7
V_IN3
20 _VIN4
9 _VIN5
18 _VIN6
V_OUTL ¹⁴
V_OUTR 15
DATA OUT ³
ACOM ¹³
11 _VIN7
16 _VIN8
SSM2163
#1
SHIELD ⁶
27 _{DATA IN}
26 _CLK
25 _WRITE
24 _LD
28 _SYSMUTE
SHIELD ⁸
SHIELD ¹⁹
SHIELD ²¹
SHIELD ²³
AGND ¹⁷
V_SS V_EE DGND
2
12 1
–5V
10µF₊
0.1µF
20k
20k
NC
5 _VIN1
+5V
4 10
+
10µF
V_DD V_CC
0.1µF
0.1µF
0.1µF
–5V
1/2 SSM2135
V_OUTL
channels of the SSM2163, as shown in Figure 27. Since any
input channel can be mixed into either or both outputs,
sophisticated pan and fade effects are easily accomplished in
software. For example, Input 1 can be connected to the left
channel with 0 dB attenuation, while Input 2 is applied to the
right channel with –10 dB of attenuation. This configuration
will produce the effect of having the audio source “located” to
the left of center line of the speakers. Another possible option
would be to attenuate the left channel while boosting the right,
which would produce an effect of movement of the audio source.
Since any input can be connected to either output, very flexible
and sophisticated effects can be produced without hardware
changes.
V_IN
V_IN1
Σ
V_OUTL
V_IN2
V_IN3
V_IN4
V_IN5
22 _VIN2
7 _VIN3
20 _VIN4
9 _VIN5
V_OUTL ¹⁴
20k
V_OUTR ¹⁵
20k
DATA OUT ³ NC
20k
V_OUTR
1/2 SSM2135
V_IN6
18 _VIN6
ACOM ¹³ NC
11
V_IN7
V_{IN7 SSM2163}
V_IN2
V_IN8
16
V_IN8
#2
SHIELD ⁶
Σ
V_OUTR
27 _{DATA IN}
SHIELD ⁸
26 _CLK
25 _WRITE
24 _LD
SHIELD ¹⁹
SHIELD ²¹
SHIELD ²³
28
SYSMUTE
AGND ¹⁷
TO INPUTS
V_SS V_EE DGND
2
12 1
–5V
SSM2163
V_IN3 – V_IN8
10µF₊
0.1µF
Figure 26. A 16-Input, 2-Output Mixer
This circuit utilizes the DATA OUT feature of the SSM2163 to
transfer data from the first SSM2163 to the second. In the
daisy-chain mode, the DATA OUT pin of the first SSM2163 is
connected to the DATA IN pin of the second device. The
advantage of this “daisy chain” connection is that it allows a
3-wire serial interface, as was used in the previous 8-input
mixer, to control two or more SSM2163s.
The serial data format for the daisy chain circuit is similar to the
8-channel application, except that the SSM2163s are loaded in
tandem. After setting WRITE and LOAD low, two bytes (16 bits)
are clocked into the first SSM2163. When WRITE and
LOAD return high, data will be latched into both SSM2163s
simultaneously.
Figure 27. Connecting the SSM2163 for Pan-Pot
Operation
Driving Headphones
A high speed, high output current amplifier, such as the OP279,
can be added to drive headphones directly. A typical connection
is shown in Figure 28. Single +5 V operation is maintained,
since the OP279 offers rail-to-rail inputs and outputs. The
OP279’s high current output stage can drive a 48 Ω load to
4 V p-p while maintaining less than 1% THD.
REV. 0
–13–