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PDF SSM2161 Data sheet ( Hoja de datos )
| Número de pieza | SSM2161 | |
| Descripción | Master/Balance Volume Controls | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de SSM2161 (archivo pdf) en la parte inferior de esta página. Total 15 Páginas | ||
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a
6- and 4-Channel, Serial Input
Master/Balance Volume Controls
SSM2160/SSM2161
FEATURES
Clickless Digitally Controlled Level Adjustment
SSM2160: Six Channels
SSM2161: Four Channels
7-Bit Master Control Gives 128 Levels of Attenuation
5-Bit Channel Controls Give 32 Levels of Gain
Master/Channel Step Size Set by External Resistors
100 dB Dynamic Range
Automatic Power On Mute
Excellent Audio Characteristics:
0.01% THD+N
0.001% IMD (SMPTE)
–90 dBu Noise Floor
–80 dB Channel Separation
90 dB SNR
Single and Dual Supply Operation
APPLICATIONS
Home Theater Receivers
Surround Sound Decoders
Circle Surround* and AC-3* Decoders
DSP Soundfield Processors
HDTV and Surround TV Audio Systems
Automotive Surround Sound Systems
Multiple Input Mixer Consoles and Amplifiers
GENERAL DESCRIPTION
The SSM2160 and SSM2161 allow digital control of volume of
six and four audio channels, respectively, with a master level
control and individual channel controls. Low distortion VCAs
(Voltage Controlled Amplifiers) are used in the signal path. By
using controlled rate-of-change drive to the VCAs, the “click-
ing” associated with switched resistive networks is eliminated in
the Master control. Each channel is controlled by a dedicated
5-bit DAC providing 32 levels of gain. A master 7-bit DAC
feeds every control port giving 128 levels of attenuation. Step
sizes are nominally 1 dB and can be changed by external
resistors. Channel balance is maintained over the entire master
control range. Upon power-up, all outputs are automatically
muted. A three- or four-wire serial data bus enables interfacing
with most popular microcontrollers. Windows* software and an
evaluation board for controlling the SSM2160 are available.
The SSM2160 can be operated from single supplies of +10 V to
+20 V or dual supplies from ± 5 V to ± 10 V. The SSM2161 can
be operated from single supplies of +8.5 V to +20 V (for
automotive applications) or dual supplies from ± 4.25 V to
± 10 V. An on-chip reference provides the correct analog
common voltage for single supply applications. Both models
come in P-DIP and SO packages. See the Ordering Guide for
more details.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
FUNCTIONAL BLOCK DIAGRAM
V+
V–
VREF
POWER
SUPPLY AND
REFERENCE
GENERATOR
5-BIT
CHANNEL
DAC
∑
5-BIT
CHANNEL
DAC
∑
5-BIT
CHANNEL
DAC
∑
5-BIT
CHANNEL
DAC
∑
5-BIT
CHANNEL
DAC
∑
CLK
DATA
LD
WRITE
5-BIT
CHANNEL
DAC
7-BIT
MASTER
DAC
SHIFT REGISTER
AND
ADDRESS
DECODER
∑
VCA
CH1 IN
CH1 OUT
VCA
CH2 IN
CH2 OUT
VCA
CH3 IN
CH3 OUT
VCA
CH4 IN
CH4 OUT
VCA
CH5 IN
CH5 OUT
VCA
CH6 IN
CH6 OUT
STEP SIZE
ADJUST
CH SET
MSTR SET
MSTR OUT
*Circle Surround is a registered trademark of Rocktron Corporation.
AC-3 is a registered trademark of Dolby Labs, Inc. Windows is a regis-
tered trademark of Microsoft Corp.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700 World Wide Web Site: http://www.analog.com
Fax: 617/326-8703
© Analog Devices, Inc., 1996
1 page  
SSM2160/SSM2161
SSM2160 SSM2161
Pin No. Pin No. Name
11
V+
22
AGND
33
VREF
44
55
66
77
8–
9–
10 8
11 9
12 10
13 11
14 12
15 13
16 –
17 –
18 14
19 15
20 16
21 17
22 18
CH1 OUT
CH1 IN
CH3 OUT
CH3 IN
CH5 OUT
CH5 IN
WRITE
LD
V–
DGND
CLK
DATA
CH6 IN
CH6 OUT
CH4 IN
CH4 OUT
CH2 IN
CH2 OUT
MSTR SET
23 19
24 20
MSTR OUT
CH SET
PIN DESCRIPTIONS
Function
V+ is the positive power supply pin. Refer to the Power Supply Connections section for more
information.
AGND is the internal ground reference for the audio circuitry. When operating the SSM2160
from dual supplies, AGND should be connected to ground. When operating from a single
supply, AGND should be connected to VREF, the internally generated voltage reference. AGND
may also be connected to an external reference. Refer to the Power Supply Connections section
for more details.
VREF is the internally generated ground reference for the audio circuitry obtained from a buffered
divider between V+ and V–. In a dual-supply application with the AGND pin connected to
ground, VREF should be left floating. In a single supply application, VREF should be connected to
AGND. Refer to the Power Supply Connections section for more details.
Audio Output from Channel 1.
Audio Input to Channel 1.
Audio Output from Channel 3.
Audio Input to Channel 3.
Audio Output from Channel 5.
Audio Input to Channel 5.
A logic LOW voltage enables the SSM2160 to receive information at the DATA input (Pin 15).
A logic HIGH applied to WRITE retains data at their previous settings. See Timing Diagrams.
Serves as CHIP SELECT.
Loads the information retained by WRITE into the SSM2160 at logic LOW. See Timing
Diagrams.
V– is the negative power supply pin. Connect to ground if using in a single supply application.
Refer to the Power Supply Connections section for more details.
DGND is the digital ground reference for the SSM2160. This pin should always be connected to
ground. All digital inputs, including WRITE, LD, CLK, and DATA are TTL input compatible;
drive currents are returned to DGND.
CLK is the clock input. It is positive edge triggered. See Timing Diagrams.
Channel and Master control information flows MSB first into the DATA pin. Refer to Address/
Data Decoding Truth Table, Figure 19, for information on how to control the VCAs.
Audio Input to Channel 6.
Audio Output from Channel 6.
Audio Input to Channel 4.
Audio Output from Channel 4.
Audio Input to Channel 2.
Audio Output from Channel 2.
MSTR SET is connected to the inverting input of an I-V converting op amp used to generate a
Master Control voltage from the Master Control DAC current output. A resistor connected
from MSTR OUT to MSTR SET reduces the step size of the Master control. See the Adjusting
Step Sizes section for more details. A 10 µF capacitor should be connected from MSTR OUT to
MSTR SET to eliminate the zipper noise in the Master control.
MSTR OUT is connected to the output of the I-V converting op amp. See MSTR SET
description.
The step size of the Channel Control can be increased by connecting a resistor from CH SET to
V+. No connection to CH SET is required if the default value of 1 dB per step is desired. Mini-
mum of 10 Ω external resistor. See the Adjusting Step Sizes section for more details.
REV. 0
–5–
5 Page 
SSM2160/SSM2161
present the attenuation and gain as two separate items, in fact,
the VCA can be operated smoothly from a gain condition to an
attenuation. The master and channel step sizes default to 1 dB
in the absence of external components. The step sizes can be
changed by the addition of external resistors if finer resolution is
desired.
Control Range vs. Step Size
Before adjusting step sizes from the standard 1 dB, consider the
effect on control range. The master control and the channel
control provide 1 dB step sizes, which may be modified by the
addition of external resistors. As the total number of steps is
unchanged, reduction of the step size results in less control
range. The range of the control is:
Range = Step Size (dB) × (Number of Levels Used)
Since the master volume control operates from a 7-bit word, its
DAC has 128 levels (including 0). The channel volume control
DAC is a 5-bit input, so there are 32 levels for volume control
(including 0). As can be seen in Figure 21, the practical control
range is set by the noise floor. It can be advantageous to reduce
the master step size to give finer steps from zero attenuation
down to the noise floor.
Reducing Master Step Size
To reduce the master step size, place a resistor, RM, between
MSTR SET and MSTR OUT. The master step size of the
master volume control will then become:
RM
= 1700 X MASTER
1 – X MASTER
where, XMASTER is the desired master control step size in
decibels. See Figure 22 for practical values of RM. Note that
the step size for the master control can only be adjusted to less
than 1 dB. No resistor is required for the default value of 1 dB
per step. For larger step sizes, use digital control. Noninteger
dB step sizes can be obtained by using digital control and a
reduced step size.
1.0
0.8
0.6
0.4
0.2
0
102 103 104 105
RMASTER
Figure 22. Master Step Size vs. RM
Example: Modifying Master Step Size to 0.5 dB
A master step size of 0.5 dB is desired for the master control,
while a 1 dB step size is adequate for the channel control. Using
the above equation or Figure 22, RM is found to be 1700 Ω and
is connected between MSTR SET and MSTR OUT. There
could be some variation from lot to lot, so applications requiring
precise step size should include a fixed plus a trimmer to span
the calculated value ± 25%. In this example, RC is not needed
as the default channel step size is already 1 dB. CH SET is left
floating. With this step size, the dynamic range of the master
control is:
DNR = 0.5 × 127 dB = 63.5 dB
In this configuration, the maximum master volume is 0 dB,
while the minimum volume is –63.5 dB. Since the channel
volume can still provide 0 dB to 31 dB of gain, the total system
gain can vary between –63.5 dB and 32 dB. Note that a 0 dB
command setting to the master control always results in unity
gain, regardless of the step size.
Channel Step Size
The channel DACs’ full-scale current is set by an internal
resistor to the V+. By shunting this resistor, the full-scale
current, and therefore the step size, will increase. No provisions
are available for reducing the channel step size. To increase the
channel step size, place a resistor, RC, from CH SET to V+.
Note that a 0 dB setting for a channel will always give unity
gain, regardless of how large or small the step size is. This is
true for both the master and channel volume controls.
1.5
1.4
1.3
1.2
1.1
1.0
101
102
RCHAN
103
Figure 23. Channel Step Size vs. RC
Example: Modifying Channel Step Size
A channel step size of 1.3 dB is desired. From Figure 23 we see
that a 40 Ω resistor (approximately) connected from CH SET to
V+ is required. As this varies from lot to lot, the exact value
should be determined empirically, or a fixed resistor plus
trimmer potentiometer should be used. Take care not to short
Pin 24 to Pin 1 as damage will result.
Muting
The SSM2160 offers master and channel muting. On power
up, the master mute is activated, thus preventing any transients
from entering the signal path and possibly overloading amplifi-
ers down the signal path. Mute is typically better than –95 dB
relative to a 0 dBu input. Due to design limitations, the individual
channel muting results in increased signal distortion in the
unmuted channels. Users should determine if this condition is
acceptable in the particular application.
REV. 0
–11–
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet SSM2161.PDF ] | |
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