SSM2160/SSM2161

–9–

REV. 0

+

+

V+

0.1µF

10µF

0.1µF

10µF

3

1

2

12

13

DGND

V–

AGND

V+

SSM2160

CHnIN

REF

OUT

Signal Chain Considerations

The SSM2160 is capable of providing an extremely wide control

range, from –127 dB of attenuation (limited only by the noise

floor) to +31 dB of gain. When configuring the system, the

SSM2160 should be in the signal chain where input signals allow

the minimum VCA gain to be used, thus ensuring the lowest

distortion operation. In consumer products, sources that

supply line level signals include FM/AM Tuner, Phono Preamp,

Cassette Deck, CD, Laserdisc, VCR, LINE, AUX and Micro-

phone Preamp. Figure 17 shows a typical application where the

SSM2160 has been placed between a surround-sound decoder

and the power amplification stages. This allows the user to

adjust both volume and balance between six speakers through the

use of the Master and Channel controls.

FM/AM TUNER

PHONO PREAMP

CASSETTE DECK

COMPACT DISK

LASER DISK

VCR

MICROPHONE

MUX

SURROUND

SOUND

DECODER

SSM2160

TO

SPEAKERS

POWER AMPS

VOLUME AND

BALANCE

CONTROLS

LINE LEVEL INPUTS – STEREO PAIRS

Figure 17. Typical Signal Chain Using the SSM2160

Digital Control Range Plan

The SSM2160 may be modelled as six ganged potentiometers

followed by individual programmable gain channel amplifiers, as

shown in Figure 18. In actuality, each channel’s signal level is

set by a VCA that can give gain or attenuation, depending upon

the control voltage supplied. The input potentiometers have a

maximum gain 0 dB (unity), a minimum gain of –127 dB, and

change in 1 dB steps. The channel amplifiers each have mini-

mum gain of 0 dB and a maximum gain of +31 dB and also

change in 1 dB steps. The data settings for the attenuation of

the master “potentiometer” and the channel “amplifier” are

shown in Table II.

OUTPUT

CHANNEL

INPUT

0dB

–127dB

31dB

0dB

MASTER

Figure 18. Potentiometer Representation of SSM2160

(One Channel Only)

Table II. Master and Channel Control

Data

dB

Hex

Binary

Master

Min Atten

0

7F

1111111

Max Atten

–127

00

0000000

Channel

Max Gain

+31

00

00000

Midgain

+15

10

10000

Min Gain

0

1F

11111

When using Channel controls as balance controls, the center

SELECTION

ADDRESS MODE

ADDRESS

DATA MODE

DATA

7-BIT MASTER DAC

5-BIT CHANNEL DAC 1

5-BIT CHANNEL DAC 2

5-BIT CHANNEL DAC 3

5-BIT CHANNEL DAC 4

5-BIT CHANNEL DAC 5

5-BIT CHANNEL DAC 6

NO DAC SELECTED

1

1

1

1

1

1

1

1

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

0

0

0

0

1

1

1

1

0

0

1

1

0

0

1

1

0

1

0

1

0

1

0

1

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

X

X

X

X

X

X

X

X = "DON'T CARE"

SHADED AREA IS DATA

0 = MUTE,

1 = UN-MUTE

MSB

MSB

LSB

LSB

XXXXX

Figure 19. Interface Characteristics, DAC Address/Data Decoding Truth Table