SSM2160/SSM2161

–8–

REV. 0

APPLICATIONS INFORMATION

General

The SSM2160 and SSM2161 are six and four channel volume

controls intended for multichannel audio applications. While

dual channel controls sufficed for “stereo” applications, the

rapidly emerging home theater “surround sound” and auto

sound venues demand both six and four channel high perfor-

mance controls. The following information applies equally to

the SSM2160 and SSM2161, except where noted. Line level

signals are fed to the six high impedance inputs. The system

microcontroller sets the gain of the six channels via a three or

four 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 17 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 six 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

±5V to

±10 V and from single supplies from +10 V to +20 V. The

SSM2161 can be operated from dual supplies from

±4.25 V to

±10 V for automotive applications and from single supplies from

+8.5 V to +20 V. In order 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 both devices. An on-chip buffered voltage divider

provides the correct analog common voltage for single supply

applications.

Table I. Signal Levels vs. Power Supplies

SSM2160

Max Output,

Max Output,

V rms (V p-p)

dBu

Dual

0.9 (2.5)

+1.3

10 V

±5 V

1.1 (3.0)

+3.0

12 V

±6 V

1.3 (3.7)

+4.5

15 V

±7.5 V

1.8 (5.0)

+7.3

20 V

±10 V

SSM2161

Max Output,

Max Output,

V rms (V p-p)

dBu

Dual

0.75 (2.1)

+1.0

8.5 V

±4.25 V

1.1 (3.0)

+3.0

12 V

±6 V

1.3 (3.7)

+4.5

15 V

±7.5 V

1.8 (5.0)

+7.3

20 V

±10 V

Dual Power Supplies

As shown in Figure 14, the AGND pin should be connected to

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 device 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.

+

1

2

V+

0.1µF

10µF

V–

10µF

12

13

DGND

V–

AGND

V+

SSM2160

+

0.1µF

Figure 14. Dual Supply Configuration

Single Power Supply

When a single supply is used, it is necessary to connect AGND

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 16 may be necessary to eliminate any

noise pickup.

+

+

V+

0.1µF

10µF

0.1µF

10µF

3

1

2

12

13

DGND

V–

AGND

V+

SSM2160

Figure 15. Single Supply Configuration