SSM2160_03 Datasheet, PDF (8/16 Pages) Analog Devices – 6-Channel, Serial Input Master/Balance Volume Controls

SSM2160
APPLICATIONS INFORMATION
General
The SSM2160 is a 6-channel volume control intended for
multichannel audio applications. While dual-channel controls
sufficed for stereo applications, rapidly emerging home theater
surround sound and auto sound venues demand both 4-channel
and 6-channel high performance controls. Line level signals are fed
to the six high impedance inputs. The system microcontroller
sets the gain of the six channels via a 3-wire or 4-wire data bus.
In a home theater receiver, the outputs may be fed to the power
amplifiers or buffered and connected to pre-out/amp-in ports on
the rear panel. Refer to Figure 5 for a typical signal chain using
the SSM2160. The master control serves the volume control
function, and the channel control serves the balance function.
The 6-channel capability allows complete control of the front left,
front right, center, rear left, rear right, and sub-bass audio channels.
Power Supplies vs. Signal Levels
The SSM2160 can be operated from dual supplies from ± 5 V to
± 10 V and from single supplies from +10 V to +20 V. To keep
power dissipation to a minimum, use the minimum power supply
voltages that will support the maximum input and output signal
levels. The peak-to-peak output signal level must not exceed 1/4
of the total power supply span, from V+ to V–. This restriction
applies for all conditions of input signal levels and gain/attenuation
settings. Table I shows supply voltages for several typical output
signal levels for the device. An on-chip buffered voltage divider
provides the correct analog common voltage for single-supply
applications.
Table I. Signal Levels vs. Power Supplies
Max Output,
V rms (V p-p)
0.9 (2.5)
1.1 (3.0)
1.3 (3.7)
1.8 (5.0)
Max Output
(dBu)
+1.3
+3.0
+4.5
+7.3
Single +V_S(V) Dual ؎V_S(V)
10
±5
12
±6
15
± 7.5
20
± 10
Dual Power Supplies
As shown in Figure 2, the AGND pin should be connected to
ground and V_REF should be left floating. The digital ground pin,
DGND, should always be connected to ground for either single-
or dual-supply configurations. Pins 1 and 12 should each have a
10 µF capacitor connected to ground, with a 0.1 µF capacitor
placed as close as possible to the SSM2160 to help reduce the
effects of high frequency power supply noise. When a switching
power supply is used, or if the power supply lines are noisy,
additional filtering of the power supply lines may be required.
V+
10␮F
0.1␮F
1
V+
SSM2160
2
AGND
VREF
V–
10␮F
12
V–
0.1␮F
13
DGND
Figure 2. Dual-Supply Configuration
Single Power Supply
When a single supply is used, it is necessary to connect AGND
(Pin 2) to V_REF (Pin 3), as shown in Figure 3. V_REF supplies a
voltage midway between the V+ and V– pins from a buffered
resistive divider. When supplying this reference to stages ahead
of the SSM2160 (to eliminate the need for input dc blocking
capacitors, for example), the use of an additional external
buffer, as shown in Figure 4, may be necessary to eliminate any
noise pickup.
V+
10␮F
10␮F
1
V+
0.1␮F
SSM2160
2
AGND
3
VREF
0.1␮F ₁₂
V–
13
DGND
Figure 3. Single-Supply Configuration
–8–
REV. A