SSM2135SZ [ADI]
Dual Single-Supply Audio Operational Amplifier; 双路单电源音频运算放大器
| 型号： | SSM2135SZ |
| 厂家： | 
ADI |
| 描述： | Dual Single-Supply Audio Operational Amplifier |
| 文件： | 总16页 (文件大小：304K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Dual Single-Supply
Audio Operational Amplifier
SSM2135
PIN CONNECTIONS
FEATURES
Excellent sonic characteristics
High output drive capability
5.2 nV/√Hz equivalent input noise @ 1 kHz
0.003% THD + N (VOUT = 1 V p-p @ 1 kHz)
3.5 MHz gain bandwidth
Unity-gain stable
OUT A
–IN A
1
2
3
4
8
7
6
5
V+
SSM2135
TOP VIEW
(Not to Scale)
OUT B
–IN B
+IN B
+IN A
V–/GND
Figure 1. 8-Lead Narrow Body SOIC (R Suffix)
Low cost
APPLICATIONS
Multimedia audio systems
Microphone preamplifiers
Headphone drivers
Differential line receivers
Balanced line drivers
Audio ADC input buffers
Audio DAC l-V converters and filters
Pseudoground generators
GENERAL DESCRIPTION
The SSM2135 dual audio operational amplifier permits excel-
lent performance in portable or low power audio systems, with
an operating supply range of 4 V to 36 V or 2 V to 1ꢀ V.
The unity-gain stable device has very low voltage noise of
5.2 nV/√Hz, and total harmonic distortion plus noise below
0.01% over normal signal levels and loads. Such characteristics
are enhanced by wide output swing and load drive capability.
A unique output stage permits output swing approaching the
rail under moderate load conditions. Under severe loading,
the SSM2135 still maintains a wide output swing with ultralow
distortion. Particularly well suited for computer audio systems
and portable digital audio units, the SSM2135 can perform
preamplification, headphone and speaker driving, and balanced
line driving and receiving. Additionally, the device is ideal for
input signal conditioning in single-supply, Σ-Δ, analog-to-
digital converter subsystems such as the AD1ꢀ77. The SSM2135
makes an ideal single-supply stereo output amplifier for audio
digital-to-analog converters (DACs) because of its low noise
and distortion.
The SSM2135 is available in an ꢀ-lead plastic SOIC package
and is guaranteed for operation over the extended industrial
temperature range of −40°C to +ꢀ5°C.
FUNCTIONAL BLOCK DIAGRAM
V+
OUTx
+INx
9V 9V
–INx
V–/GND
Figure 2.
Rev. G
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2003–2011 Analog Devices, Inc. All rights reserved.
SSM2135
TABLE OF CONTENTS
Features .............................................................................................. 1
Thermal Resistance.......................................................................4
ESD Caution...................................................................................4
Typical Performance Characteristics ..............................................5
Applications Information.............................................................. 10
Application Circuits................................................................... 10
Outline Dimensions....................................................................... 14
Ordering Guide .......................................................................... 14
Applications....................................................................................... 1
Pin Connections ............................................................................... 1
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
REVISION HISTORY
4/11—Rev. F to Rev. G
Changes to Figure 36...................................................................... 12
Changes to Applications Information Section, Low Noise Stereo
Headphone Driver Amplifier Section, Figure 31, and Figure 32
........................................................................................................... 10
Changes to Low Noise Microphone Preamplifier Section,
2/09—Rev. E to Rev. F
Updated Format..................................................................Universal
Changes to Features Section, General Description Section, and
Figure 1 Caption ............................................................................... 1
Changes to Specifications Section Conditions ............................. 3
Changed AVO Symbol to AV ............................................................. 3
Changes to Supply Current Parameter, Table 1............................ 3
Deleted ESD Ratings Table.............................................................. 3
Changes to Figure 4 and Figure 5................................................... 5
Changes to Figure 9.......................................................................... 6
Changes to Figure 15, Figure 13, and Figure 18 ........................... 7
Changes to Figure 21, Figure 24 Caption, and Figure 25............ 8
Changes to Figure 27 and Figure 28............................................... 9
Deleted Figure 5; Renumbered Sequentially............................... 10
Deleted 18-Bit Stereo CD-DAC Output Amplifier Section...... 10
Figure 33, and Figure 34 ................................................................ 11
Changes to Figure 37...................................................................... 12
Deleted Spice Macromodel Section ............................................. 12
Changes to Digital Volume Control Circuit Section, Figure 38,
and Figure 39................................................................................... 13
Updated Outline Dimensions....................................................... 14
Changes to Ordering Guide.......................................................... 14
2/03—Rev. D to Rev. E
Removed 8-Lead Plastic DIP Package .............................Universal
Edits to Thermal Characteristics.....................................................4
Edits to Outline Dimensions......................................................... 14
Updated Ordering Guide .............................................................. 14
Rev. G | Page 2 of 16
SSM2135
SPECIFICATIONS
VS = 5 V, −40°C ≤ TA ≤ +85°C, unless otherwise noted. Typical specifications apply at TA = 25°C.
Table 1.
Parameter
Symbol
Conditions
Min Typ
Max Unit
AUDIO PERFORMANCE
Voltage Noise Density
Current Noise Density
Signal-To-Noise Ratio
Headroom
en
in
f = 1 kHz
f = 1 kHz
5.2
0.5
121
5.3
nV/√Hz
pA/√Hz
dBu
SNR
HR
THD + N
20 Hz to 20 kHz, 0 dBu = 0.775 V rms
Clip point = 1% THD + N, f = 1 kHz, RL = 10 kΩ
AV = +1, VOUT = 1 V p-p, f = 1 kHz, 80 kHz LPF
RL = 10 kΩ
dBu
Total Harmonic Distortion Plus Noise
0.003
0.005
%
%
RL = 32 Ω
DYNAMIC PERFORMANCE
Slew Rate
Gain Bandwidth Product
Settling Time
SR
GBW
tS
RL = 2 kΩ, TA = 25°C
To 0.1%, 2 V Step
0.6
0
0.9
3.5
5.8
V/μs
MHz
μs
INPUT CHARACTERISTICS
Input Voltage Range
Input Offset Voltage
Input Bias Current
Input Offset Current
Differential Input Impedance
Common-Mode Rejection
Large Signal Voltage Gain
OUTPUT CHARACTERISTICS
Output Voltage Swing High
VCM
VOS
IB
4.0
2.0
750
50
V
VOUT = 2 V
VCM = 0 V, VOUT = 2 V
VCM = 0 V, VOUT = 2 V
0.2
300
mV
nA
nA
MΩ
dB
IOS
ZIN
CMR
AV
4
112
0 V ≤ VCM ≤ 4 V, f = dc
0.01 V ≤ VOUT ≤ 3.9 V, RL = 600 Ω
87
2
V/μV
VOH
VOL
ISC
RL = 100 kΩ
RL = 600 Ω
RL = 100 kΩ
RL = 600 Ω
4.1
3.9
V
V
mV
mV
mA
Output Voltage Swing Low
3.5
3.0
Short-Circuit Current Limit
POWER SUPPLY
30
Supply Voltage Range
VS
Single supply
Dual supply
4
36
18
V
V
2
Power Supply Rejection Ratio
Supply Current
PSRR
ISY
VS = 4 V to 6 V, f = dc
VS = 5 V, VOUT = 2.0 V, no load
VS = 18 V, VOUT = 0 V, no load
90
120
2.8
3.7
dB
mA
mA
6.0
7.6
Rev. G | Page 3 of 16
SSM2135
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
THERMAL RESISTANCE
Rating
Supply Voltage
Single Supply
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
36 V
Dual Supply
Input Voltage
18 V
VS
10 V
Indefinite
−65°C to +150°C
−40°C to +85°C
−65°C to +150°C
300°C
Table 3.
Package Type
θJA
θJC
Unit
Differential Input Voltage
Output Short-Circuit Duration
Storage Temperature Range
Operating Temperature Range
Junction Temperature Range (TJ)
Lead Temperature (Soldering, 60 sec)
8-Lead SOIC (R-8)
158
43
°C/W
ESD CAUTION
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Rev. G | Page 4 of 16
SSM2135
TYPICAL PERFORMANCE CHARACTERISTICS
10
1
V
A
= 5V
= +1
S
V
f = 1kHz
V
= 1V p-p
= 10kΩ
IN
R
L
80kHz LOW-PASS FILTER
0.1
5V
500µF
0.01
0.001
R
L
10
100
1k
10k
LOAD RESISTANCE (Ω)
2.5V DC
Figure 6. THD + N vs. Load (See Figure 3)
Figure 3. Test Circuit for Figure 4, Figure 5, and Figure 6
1
1
A
= +1
= 5V
V = 5V
S
f = 1kHz
V
V
S
f = 1kHz
80kHz LOW-PASS FILTER
V = 2.5V p-p
OUT
= 100kΩ
NONINVERTING
R
L
80kHz LOW-PASS FILTER
R
= 32Ω
L
0.1
0.1
0.01
R
= 10kΩ
L
0.01
INVERTING
0.001
0.0005
0.001
50m
0.1
1
5
0
10
20
30
GAIN (dB)
40
50
60
INPUT VOLTAGE (V p-p)
Figure 4. THD + N vs. Amplitude (See Figure 3)
Figure 7. THD + N vs. Gain
1
1
A
V
= +1
= 5V
= 1V p-p
V
A
= 5V
= +1
V
S
S
V
V
f = 1kHz
IN
80kHz LOW-PASS FILTER
V
= 1V p-p
IN
R
= 10kΩ
L
80kHz LOW-PASS FILTER
0.1
0.1
R
= 32Ω
L
0.01
0.01
0.001
R
= 10kΩ
L
0.001
0.0005
0
5
10
15
20
25
30
20
100
1k
FREQUENCY (Hz)
10k
20k
SUPPLY VOLTAGE (V)
Figure 8. THD + N vs. Supply Voltage
Figure 5. THD + N vs. Frequency (See Figure 3)
Rev. G | Page 5 of 16
SSM2135
10
5
4
3
2
1
0
V
A
= 5V
= +1
V
T
= 5V
= 25°C
S
S
V
A
f = 1kHz
R
= 10kΩ
L
1
0.1
0.01
0.001
50m
0.1
1
5
1
10
100
FREQUENCY (Hz)
1k
AMPLITUDE (V p-p)
Figure 9. SMPTE Intermodulation Distortion
Figure 12. Current Noise Density vs. Frequency
2.0
A
= +1
= 5V
= 1V p-p
= 10kΩ
V
S
V
V
1.5
1.0
IN
1s
R
L
100
90
0.5
0
–0.5
–1.0
–1.5
–2.0
10
0%
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 10. Input Voltage Noise (20 nV/Div)
Figure 13. Frequency Response
30
V
T
= 5V
= 25°C
S
A
5µs
5µs
25
20
15
10
5
100
90
10
0%
0
20mV
20mV
1
10
100
FREQUENCY (Hz)
1k
Figure 11. Voltage Noise Density vs. Frequency
Figure 14. Square Wave Response (VS = 5 V, AV = +1, RL = ∞)
Rev. G | Page 6 of 16
SSM2135
60
40
50
40
V
T
R
= 5V
= 25°C
= 10kΩ
V
T
= 5V
= 25°C
S
A
S
A
A
A
A
= +100
= +10
= +1
V
V
V
L
20
30
0
–20
–40
–60
–80
–100
–120
–140
20
10
0
–10
–20
–105
10
100
1k
10k
100k
1M
10M
1k
10k
100k
1M
10M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 15. Crosstalk vs. Frequency
Figure 18. Closed-Loop Gain vs. Frequency
140
120
100
80
100
80
60
40
20
0
V
T
= 5V
= 25°C
V
T
= 5V
= 25°C
S
S
A
A
0
45
GAIN
90
PHASE
60
135
180
225
40
20
0
100
–20
1k
1k
10k
100k
1M
10k
100k
FREQUENCY (Hz)
1M
10M
FREQUENCY (Hz)
Figure 16. Common-Mode Rejection vs. Frequency
Figure 19. Open-Loop Gain and Phase vs. Frequency
140
120
100
80
50
V
= 5V
= +1
= 25°C
V
= 5V
S
S
A
R = 2kΩ
V
A
45
40
35
30
25
20
15
10
5
L
T
V
= 100mV p-p
= 25°C
= +1
IN
A
T
A
V
+PSRR
NEGATIVE EDGE
60
–PSRR
40
POSITIVE EDGE
20
0
–20
10
0
100
1k
10k
100k
1M
0
100
200
300
400
500
FREQUENCY (Hz)
LOAD CAPACITANCE (pF)
Figure 17. Power Supply Rejection Ratio vs. Frequency
Figure 20. Small Signal Overshoot vs. Load Capacitance
Rev. G | Page 7 of 16
SSM2135
50
40
35
30
25
20
15
10
5
V
A
R
= 5V
= +1
= 10kΩ
V
T
= 5V
= 25°C
S
S
V
L
45
40
35
30
25
20
15
10
5
A
f = 1kHz
THD + N = 1%
T
= 25°C
A
A
= +100
V
A
= +10
V
A
= +1
V
0
0
10
100
1k
10k
100k
1M
0
5
10
15
20
25
30
35
40
FREQUENCY (Hz)
SUPPLY VOLTAGE (V)
Figure 21. Output Impedance vs. Frequency
Figure 24. Output Voltage vs. Supply Voltage
5.0
4.5
4.0
3.5
3.0
2.0
5
4
3
2
1
0
V
= 5V
= 25°C
= +1
V
= 5V
S
S
T
A
A
V
f = 1kHz
THD + N = 1%
1.5
1.0
0.5
0
+SWING
L
R
= 2kΩ
+SWING
R
= 600Ω
–SWING
= 2kΩ
L
R
L
–SWING
= 600Ω
R
L
–75
–50
–25
0
25
50
75
100
125
1
10
100
1k
10k
100k
TEMPERATURE (°C)
LOAD RESISTANCE (Ω)
Figure 25. Output Swing vs. Temperature and Load
Figure 22. Maximum Output Voltage vs. Load Resistance
6
5
4
3
2
1
0
2.0
1.5
1.0
0.5
0
V
R
= 5V
S
V
= 5V
S
= 2kΩ
= 25°C
= +1
L
0.5V ≤ V
≤4V
OUT
T
A
A
V
+SLEW RATE
–SLEW RATE
1k
10k
100k
1M
10M
–75
–50
–25
0
25
50
75
100
125
FREQUENCY (Hz)
TEMPERATURE (°C)
Figure 23. Maximum Output Swing vs. Frequency
Figure 26. Slew Rate vs. Temperature
Rev. G | Page 8 of 16
SSM2135
20
18
16
14
12
10
8
5
4
3
2
1
0
V
V
= 5V
S
= 3.9V
OUT
R
= 2kΩ
L
V
= ±18V
S
V
= ±15V
S
R
= 600Ω
L
V
= +5V
S
6
4
2
0
–75
–50
–25
0
25
50
75
100
125
–75
–50
–25
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 27. Open-Loop Gain vs. Temperature
Figure 29. Supply Current vs. Temperature
70
65
60
55
50
5
4
3
2
1
500
400
300
200
100
0
V
= 5V
S
V
= +5V
S
GBW
V
= ±15V
S
Φ
m
–75
–50
–25
0
25
50
75
100
125
–75
–50
–25
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 28. Gain Bandwidth Product and Phase Margin vs. Temperature
Figure 30. Input Bias Current vs. Temperature
Rev. G | Page 9 of 16
SSM2135
APPLICATIONS INFORMATION
The SSM2135 is a low voltage audio amplifier that has exception-
ally low noise and excellent sonic quality even when driving loads
as small as 25 Ω. Designed for single supply use, the inputs and
output can both swing very close to 0 V. Thus with a supply
voltage at 5 V, both the input and output swing from 0 V to 4 V.
Because of this, signal dynamic range can be optimized if the
amplifier is biased to a 2 V reference rather than at half the
supply voltage.
10kΩ
8.66kΩ
40
L_OUT
2
3
35/36
470µF
5V
0.1µF
V
CC
1
1/2
SSM2135
34/37
32
GNDA
LEFT
V+
CHANNEL
10µF
V
REF
0.1µF
10µF
RIGHT
CHANNEL
0.1µF
7
8
4
5
6
AGND
AD1845
R_OUT
1/2
SSM2135
470µF
The SSM2135 is unity-gain stable, even when driving into a fair
amount of capacitive load. Driving up to 500 pF does not cause
any instability in the amplifier. However, overshoot in the
frequency response increases slightly.
41
10kΩ
8.66kΩ
Figure 31. A Stereo Headphone Driver for Multimedia Sound Codec
The SSM2135 makes an excellent output amplifier for 5 V only
audio systems such as a multimedia workstation, a CD output
amplifier, or an audio mixing system. The amplifier has large
output swing even at this supply voltage because it is designed
to swing to the negative rail. In addition, it easily drives load
impedances as low as 25 Ω with low distortion.
Figure 32 shows the total harmonic distortion characteristics vs.
frequency driving into a 32 Ω load, which is a very typical
impedance for a high quality stereo headphone. The SSM2135
has excellent power supply rejection, and, as a result, is tolerant
of poorly regulated supplies. However, for best sonic quality, the
power supply should be well regulated and heavily bypassed to
minimize supply modulation under heavy loads. A minimum of
10 μF bypass is recommended.
The SSM2135 is fully protected from phase reversal for inputs
going to the negative supply rail. However, internal ESD protec-
tion diodes turn on when either input is forced more than 0.5 V
below the negative rail. Under this condition, input current in
excess of 2 mA may cause erratic output behavior, in which case,
a current limiting resistor should be included in the offending
input if phase integrity is required with excessive input voltages.
A 500 Ω or higher series input resistor prevents phase inversion
even with the input pulled 1 V below the negative supply.
1
V
= 5V
S
80kHz LOW-PASS FILTER
0.1
0.01
Hot plugging the input to a signal generally does not present a
problem for the SSM2135, assuming that the signal does not
have any voltage exceeding the supply voltage of the device.
If so, it is advisable to add a series input resistor to limit the
current, as well as a Zener diode to clamp the input to a voltage
no higher than the supply.
0.001
0.005
10
100
1k
FREQUENCY (Hz)
10k 20k
APPLICATION CIRCUITS
Figure 32. Headphone Driver THD + N vs. Frequency into a 32 Ω Load
Low Noise Stereo Headphone Driver Amplifier
Figure 31 shows the SSM2135 used in a stereo headphone driver
for multimedia applications with the AD1845, a 16-bit stereo
codec. The SSM2135 is equally well suited for the serial-bused
AD1849 stereo codec. The impedance of the headphone can be
as low as 25 Ω, which covers most commercially available high
fidelity headphones. Although the amplifier can operate at up to
18 V supply, it is just as efficient powered by a single 5 V. At
this voltage, the amplifier has sufficient output drive to deliver
distortion-free sound to a low impedance headphone.
Rev. G | Page 10 of 16
SSM2135
1
Low Noise Microphone Preamplifier
V
A
= 5V
= 40dB
S
V
The 5.2 nV/√Hz input noise in conjunction with low distortion
make the SSM2315 an ideal device for amplifying low level signals
such as those produced by microphones. Figure 34 illustrates a
stereo microphone input circuit feeding a multimedia sound
codec. The gain is set at 100 (40 dB), although it can be set to
other gains depending on the microphone output levels. Figure 33
shows the harmonic distortion performance of the preamplifier
with 1 V rms output, while operating from a single 5 V supply.
V
= 1V rms
OUT
80kHz LOW-PASS FILTER
0.1
The SSM2135 is biased to 2.25 V by the VREF pin of the AD1845
codec. The same voltage is buffered by the 2N4124 transistor to
provide phantom power to the microphone. A typical electrets
condenser microphone with an impedance range of 100 Ω to
1 kΩ works well with the circuit. This power booster circuit can
be omitted for dynamic microphone elements.
0.01
10
100
1k
FREQUENCY (Hz)
10k 20k
Figure 33. MIC Preamp THD + N Performance
10kΩ
5V
10µF
100Ω
LEFT CHANNEL
MIC IN
8
2
3
29
L_MIC
35/36
1
10µF
1/2
SSM2135
5V
V
CC
4
10kΩ
5V
2kΩ
0.1µF
34/37
GNDA
2N4124
32
V
REF
10µF
0.1µF
7
10kΩ
10µF
RIGHT CHANNEL
MIC IN
AD1845
2kΩ
5
6
28
R_MIC
1/2
SSM2135
100Ω
10kΩ
Figure 34. Low Noise Microphone Preamp for Multimedia Sound Codec
Rev. G | Page 11 of 16
SSM2135
Single Supply Differential Line Driver
Pseudoreference Voltage Generator
Signal distribution and routing is often required in audio systems,
particularly portable digital audio equipment for professional
applications. Figure 35 shows a single-supply line driver circuit
that has differential output. The bottom amplifier provides a
2 V dc bias for the differential amplifier to maximize the output
swing range. The amplifier can output a maximum of 0.8 V rms
signal with a 5 V supply. It is capable of driving into 600 Ω line
termination at a reduced output amplitude.
For single-supply circuits, a reference voltage source is often
required for biasing purposes or signal offsetting purposes. The
circuit in Figure 37 provides a supply splitter function with low
output impedance. The 1 μF output capacitor serves as a charge
reservoir to handle a sudden surge in demand by the load as
well as providing a low ac impedance to it. The 0.1 μF feedback
capacitor compensates the amplifier in the presence of a heavy
capacitive load, maintaining stability.
1kΩ
The output can source or sink up to 12 mA of current with a
5 V supply, limited only by the 100 Ω output resistor. Reducing
the resistance increases the output current capability. Alternatively,
increasing the supply voltage to 12 V also improves the output
drive to more than 25 mA.
5V
10µF + 0.1µF
1/2
SSM2135
100µF
AUDIO IN
DIFFERENTIAL
AUDIO OUT
V+ = 5V TO 12V
1kΩ
R3
2.5kΩ
1kΩ
10kΩ
1/2
SSM2135
C1
0.1µF
R1
5kΩ
2V
2.5kΩ
R4
100kΩ
5V
1/2
SSM2135
V+
2
OUTPUT
0.1µF
5V
C2
1µF
100Ω
R2
5kΩ
1/2
SSM2135
7.5kΩ
1µF
5kΩ
Figure 37. Pseudoreference Generator
Figure 35. Single-Supply Differential Line Driver
Single-Supply Differential Line Receiver
Receiving a differential signal with minimum distortion is
achieved using the circuit in Figure 36. Unlike a difference
amplifier (a subtractor), the circuit has a true balanced input
impedance regardless of input drive levels; that is, each input
always presents a 20 kΩ impedance to the source. For best
common-mode rejection performance, all resistors around the
differential amplifier must be very well matched. Best results
can be achieved using a 10 kΩ precision resistor network.
20kΩ
5V
10µF + 0.1µF
20kΩ
20kΩ
1/2
SSM2135
20kΩ
20kΩ
DIFFERENTIAL
AUDIO IN
10µF
10Ω
1/2
SSM2135
2V
AUDIO
OUT
5V
1µF
7.5kΩ
5V
100Ω
1/2
SSM2135
5kΩ
0.1µF
2.5kΩ
Figure 36. Single-Supply Balanced Differential Line Receiver
Rev. G | Page 12 of 16
SSM2135
Digital Volume Control Circuit
Logarithmic Volume Control Circuit
Working in conjunction with the AD7528 dual 8-bit DAC,
the SSM2135 makes an efficient audio attenuator, as shown in
Figure 38. The circuit works off a single 5 V supply. The DACs
are biased to a 2 V reference level, which is sufficient to keep
the internal R-2R ladder switches of the DACs operating prop-
erly. This voltage is also the optimal midpoint of the SSM2135
common-mode and output swing range. With the circuit as
shown in Figure 38, the maximum input and output swing is
1.25 V rms. Total harmonic distortion measures a respectable
0.01% at 1 kHz and 0.1% at 20 kHz. The frequency response at
any attenuation level is flat to 20 kHz.
Figure 39 shows a logarithmic version of the volume control
function. Similar biasing is used. With an 8-bit bus, the AD7111
provides an 88.5 dB attenuation range. Each bit resolves a 0.375 dB
attenuation. Refer to the AD7111 data sheet for attenuation levels
for each input code.
5V
0.1µF
5V
10µF + 0.1µF
3
14
16
47µF
10
DGND
V
R
FB
DD
1
2
LEFT AUDIO
IN
V
I
IN
OUT
1/2
SSM2135
LEFT AUDIO
OUT
AD7111
47µF
AGND
D1
5V
0.1µF
Each DAC can be controlled independently via the 8-bit parallel
data bus. The attenuation level is linearly controlled by the
binary weighting of the digital data input. Total attenuation
ranges from 0 dB to 48 dB.
3
14
16
47µF
10
DGND
V
R
DD
FB
1
2
RIGHT AUDIO
IN
I
V
OUT
IN
1/2
SSM2135
RIGHT AUDIO
OUT
AD7111
47µF
AGND
D1
3
2kΩ
DATA IN
AND
CONTROL
AD7528
5V
10µF + 0.1µF
10
5V
5V
R
A
0.1µF
100Ω
FB
OUT A
2
LEFT
AUDIO IN
V
A
REF
1/2
SSM2135
7.5kΩ
LEFT AUDIO
OUT
1/2
SSM2135
DAC A
2V
2V
47µF
1µF
5kΩ
DATA IN
Figure 39. Single-Supply Logarithmic Volume Control
6
DAC A/
DAC B
CONTROL
SIGNAL
15
16
CS
19
WR
R
B
FB
20
1
RIGHT
AUDIO IN
18
V
B
OUT B
REF
1/2
SSM2135
RIGHT AUDIO
OUT
DACB
47µF
2kΩ
V
DGND
5
DD
17
5V
5V
0.1µF
100Ω
7.5kΩ
1/2
SSM2135
0.1µF
2V
2V
5V
1µF
5kΩ
Figure 38. Digital Volume Control
Rev. G | Page 13 of 16
SSM2135
OUTLINE DIMENSIONS
5.00 (0.1968)
4.80 (0.1890)
8
1
5
4
6.20 (0.2441)
5.80 (0.2284)
4.00 (0.1574)
3.80 (0.1497)
0.50 (0.0196)
0.25 (0.0099)
1.27 (0.0500)
BSC
45°
1.75 (0.0688)
1.35 (0.0532)
0.25 (0.0098)
0.10 (0.0040)
8°
0°
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
1.27 (0.0500)
0.40 (0.0157)
0.25 (0.0098)
0.17 (0.0067)
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MS-012-AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 40. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
ORDERING GUIDE
Model1
Temperature Range
−40°C to +85°C
Package Description
Package Option
SSM2135S
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
R-8
R-8
R-8
R-8
R-8
R-8
SSM2135S-REEL
SSM2135S-REEL7
SSM2135SZ
SSM2135SZ-REEL
SSM2135SZ-REEL7
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
1 Z = RoHS Compliant Part.
Rev. G | Page 14 of 16
SSM2135
NOTES
Rev. G | Page 15 of 16
SSM2135
NOTES
©2003–2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00349-0-4/11(G)
Rev. G | Page 16 of 16
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