REV. A

SSM2160

–9–

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 = UNMUTE

MSB

MSB

LSB

LSB

XXXXX

Figure 7. Interface Characteristics, DAC Address/Data Decoding Truth Table

+

+

V+

0.1 F

10 F

0.1 F

10 F

3

1

2

12

13

DGND

V–

AGND

V+

SSM2160

CHn IN

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, laser disk, VCR, LINE, AUX, and microphone preamp.

Figure 5 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 5. Typical Signal Chain Using the SSM2160

Digital Control Range Plan

The SSM2160 may be modeled as six ganged potentiometers

followed by individual programmable gain channel amplifiers, as

shown in Figure 6. 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

1dB steps. The channel amplifiers each have minimum 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 6. 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 would

be with Channel = 10h (or 0Fh if desired). Increasing the gain

to the maximum would occur at Channel = 00h. Reducing the

gain to minimum would occur at Channel = 1Fh.