SSM2160_03 Datasheet, PDF (9/16 Pages) Analog Devices – 6-Channel, Serial Input Master/Balance Volume Controls

SSM2160
V+
10␮F
1
V+
0.1␮F
SSM2160
2
AGND
CHn IN
REF
OUT
10␮F
0.1␮F
3 ^VREF
12 _V–
13
DGND
Figure 4. Single-Supply Operation with V_REF Buffer
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
LINE LEVEL INPUTS – STEREO PAIRS
POWER AMPS
SSM2160
VOLUME AND
BALANCE
CONTROLS
TO
SPEAKERS
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
1 dB 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.
INPUT
MASTER
0dB
–127dB
OUTPUT
+31dB 0dB
CHANNEL
Figure 6. Potentiometer Representation of SSM2160
(One Channel Only)
Table II. Master and Channel Control
Master
Channel
Min Atten
Max Atten
Max Gain
Midgain
Min Gain
dB
0
–127
+31
+15
0
Data
Hex
7F
00
00
10
1F
Binary
1111111
0000000
00000
10000
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.
SELECTION
MSB
LSB MSB
ADDRESS MODE
ADDRESS
LSB
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
1XXXX0 0 0 0
1XXXX0 0 1 01X
1XXXX0 1 0 01X
1XXXX0 1 1 01X
1XXXX1 0 0 01X
1XXXX1 0 1 01X
1XXXX1 1 0 01X
1XXXX1 1 1 01X
XXXXX
X = DON'T CARE
SHADED AREA IS DATA
0 = MUTE
1 = UNMUTE
Figure 7. Interface Characteristics, DAC Address/Data Decoding Truth Table
REV. A
–9–