AD SSM2135_03

Dual Single-Supply
Audio Operational Amplifier
SSM2135*
FEATURES
Excellent Sonic Characteristics
High Output Drive Capability
5.2 nV/÷Hz Equivalent Input Noise @ 1 kHz
0.001% THD+N (VO = 2.5 V p-p @ 1 kHz)
3.5 MHz Gain Bandwidth
Unity-Gain Stable
Low Cost
PIN CONNECTIONS
8-Lead Narrow-Body SOIC
(S Suffix)
V+
OUT A
–IN A
SSM-2135
OUT B
+IN A
–IN B
V–/GND
+IN B
APPLICATIONS
Multimedia Audio Systems
Microphone Preamplifier
Headphone Driver
Differential Line Receiver
Balanced Line Driver
Audio ADC Input Buffer
Audio DAC l-V Converter and Filter
Pseudo-Ground Generator
GENERAL DESCRIPTION
The SSM2135 Dual Audio Operational Amplifier permits excellent performance in portable or low power audio systems, with
an operating supply range of +4 V to +36 V or ± 2 V to ± 18 V.
The unity gain stable device has very low voltage noise of
4.7 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, sigma-delta, analog-to-digital converter
subsystems such as the AD1878/AD1879.
The SSM2135 is available in an 8-lead plastic SOIC package
and is guaranteed for operation over the extended industrial
temperature range of –40∞C to +85∞C.
FUNCTIONAL BLOCK DIAGRAM
V+
OUT
+IN
9V 9V
–IN
V–/GND
*Protected by U.S. Patent No. 5,146,181.
REV. E
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. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
SSM2135–SPECIFICATIONS
(VS = 5 V, –40ⴗC < TA < +85ⴗC, unless otherwise noted.
Typical specifications apply at TA = +25ⴗC.)
Parameter
Symbol
Conditions
AUDIO PERFORMANCE
Voltage Noise Density
Current Noise Density
Signal-To-Noise Ratio
Headroom
Total Harmonic Distortion
en
in
SNR
HR
THD+N
f = 1 kHz
f = 1 kHz
20 Hz to 20 kHz, 0 dBu = 0.775 V rms
Clip Point = 1% THD+N, f = 1 kHz, RL = 10 kW
AV = +1, VO = 1 V p-p, f = 1 kHz, 80 kHz LPF
RL = 10 kW
RL = 32 W
DYNAMIC PERFORMANCE
Slew Rate
Gain Bandwidth Product
Settling Time
SR
GBW
tS
INPUT CHARACTERISTICS
Input Voltage Range
Input Offset Voltage
Input Bias Current
Input Offset Current
Differential Input Impedance
Common-Mode Rejection
Large Signal Voltage Gain
VCM
VOS
IB
IOS
ZIN
CMR
AVO
OUTPUT CHARACTERISTICS
Output Voltage Swing High
VOH
Output Voltage Swing Low
VOL
Short Circuit Current Limit
ISC
POWER SUPPLY
Supply Voltage Range
Power Supply Rejection Ratio
Supply Current
VS
PSRR
ISY
Min
RL = 2 kW, TA = 25∞C
0.6
To 0.1%, 2 V Step
Typ
nV/÷Hz
pA/÷Hz
dBu
dBu
0.003
0.005
%
%
0.9
3.5
5.8
V/ms
MHz
ms
0.2
300
0 V £ VCM £ 4 V, f = dc
0.01 V £ VOUT £ 3.9 V, RL = 600 W
87
2
RL = 100 kW
RL = 600 W
RL = 100 kW
RL = 600 W
4.1
3.9
Single Supply
Dual Supply
VS = 4 V to 6 V, f = dc
VOUT = 2.0 V, No Load
VS = 5 V
VS = ± 18 V, VOUT = 0 V, No Load
4
±2
90
Unit
5.2
0.5
121
5.3
0
VOUT = 2 V
VCM = 0 V, VOUT = 2 V
VCM = 0 V, VOUT = 2 V
Max
4.0
2.0
750
50
4
112
± 30
120
2.8
3.7
3.5
3.0
V
mV
nA
nA
MW
dB
V/mV
V
V
mV
mV
mA
36
± 18
V
V
dB
6.0
7.6
mA
mA
Specifications subject to change without notice.
–2–
REV. E
SSM2135
THERMAL CHARACTERISTICS
ABSOLUTE MAXIMUM RATINGS
Supply Voltage
Single Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 V
Dual Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± VS
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . 10 V
Output Short Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range . . . . . . . . . . . . . –65∞C to +150∞C
Operating Temperature Range . . . . . . . . . . . . –40∞C to +85∞C
Junction Temperature Range (TJ) . . . . . . . . . –65∞C to +150∞C
Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . . 300∞C
Thermal Resistance*
qJA
qJC
8-Lead SOIC
*qJA is specified for worst case conditions, i.e., qJA is specified for device soldered in circuit board for SOIC package.
ORDERING GUIDE
ESD RATINGS
Model
Temperature
Range
Package
Description
Package
Option
SSM2135S
–40∞C to +85∞C
8-Lead SOIC
SOIC-8
883 (Human Body) Model . . . . . . . . . . . . . . . . . . . . . . . . 1 kV
EIAJ Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 V
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
SSM2135 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.
REV. E
158∞C/W
43∞C/W
–3–
SSM2135–Typical Performance Characteristics
10
VS = 5V
AV = +1, F = 1kHz
VIN = 1V p-p
RL = 10k⍀
WITH 80kHz FILTER
1
5V
THD – %
500␮F
RL
0.1
0.01
2.5Vdc
0.001
100
1k
LOAD RESISTANCE – ⍀
10
Test Circuit 1. Test Circuit for TPCs 1, 2, and 3
AUDIO PRECISION
1
TPC 3. THD+N vs. Load (See Test Circuit)
THD+N(%) VS. AMPL(V p-p)
1
VS = 5V
RL = 100k⍀
VOUT = 2.5V p-p
f = 1kHz
WITH 80kHz FILTER
0.1
RL = 32⍀
NONINVERTING
THD+N – %
0.1
RL = 10k⍀
0.010
10k
INVERTING
0.01
0.001
0.0005
50m
0.1
1
0.001
0
5
10
TPC 1. THD+N vs. Amplitude (See Test Circuit 1; AV = +1,
VS = 5 V, f = 1 kHz, with 80 kHz Low-Pass Filter)
AUDIO PRECISION
1
20
30
GAIN – dB
40
50
60
TPC 4. THD+N vs. Gain
THD+N(%) VS. FREQ(Hz)
1
0.1
VS = 5V
AV = +1, f = 1kHz
VIN = 1V p-p
RL = 10k⍀
WITH 80kHz FILTER
THD+N – %
0.1
RL = 32⍀
0.010
0.01
RL = 10k⍀
0.001
0.001
0.0005
20
100
1k
10k
5
20k
10
15
20
SUPPLY VOLTAGE – V
25
30
TPC 5. THD+N vs. Supply Voltage
TPC 2. THD+N vs. Frequency (See Test Circuit 1;
AV = +1, VIN = 1 V p-p, with 80 kHz Low-Pass Filter)
–4–
REV. E
SSM2135
AUDIO PRECISION
10
SMPTE(%) VS AMPL(V p-p)
5
VS = 5V
TA = 25ⴗC
4
in – pA/ Hz
1
0.1
3
2
0.010
1
0
0.001
50m
0.1
1
1
5
TPC 6. SMPTE Intermodulation Distortion (AV = +1,
VS = 5 V, f = 1 kHz, RL = 10 kW)
10
100
FREQUENCY – Hz
1k
TPC 9. Current Noise Density vs. Frequency
AUDIO PRECISION
2.0000
AMPL(dBu) VS FREQ(Hz)
1.5000
1S
1.0000
100
90
0.5000
0.0
–0.500
10
0%
–1.000
–1.500
–2.000
20
TPC 7. Input Voltage Noise (20 nV/div)
100
1k
10k
100k
TPC 10. Frequency Response (AV = +1, VS = 5 V,
VIN = 1 V p-p, RL = 10 kW)
30
VS = 5V
TA = 25ⴗC
25
5µs
5µs
20mV
20mV
100
90
en – nV/ Hz
20
15
10
10
0%
5
0
1
10
100
FREQUENCY – Hz
1k
TPC 8. Voltage Noise Density vs. Frequency
REV. E
TPC 11. Square Wave Response (VS = 5 V, AV = +1,
RL = •)
–5–
SSM2135
50
60
VS = 5V
TA = 25ⴗC
VS = 5V
TA = 25ⴗC
40
AV = +100
20
CLOSED-LOOP GAIN – dB
CHANNEL SEPARATION – dB
40
0
–20
–40
–60
–80
30
20
AV = +10
10
0
AV = +1
–100
105
–10
–120
100
1k
10k
100k
FREQUENCY – Hz
1M
–20
1k
10M
TPC 12. Crosstalk vs. Frequency (RL = 10 kW)
10M
1M
100
VS = 5V
TA = 25ⴗC
VS = 5V
TA = 25ⴗC
120
80
100
80
60
40
20
0
100
1k
10k
FREQUENCY – Hz
0
60
45
GAIN
40
90
PHASE
20
135
0
180
–20
1k
1M
100k
TPC 13. Common-Mode Rejection vs. Frequency
10k
100k
FREQUENCY – Hz
225
10M
1M
TPC 16. Open-Loop Gain and Phase vs. Frequency
50
140
VS = 5V
AV = +1
TA = 25ⴗC
120
VS = 5V
RL = 2k⍀
VIN = 100mV p-p
TA = 25ⴗC
AV = +1
45
40
OVERSHOOT – %
100
PSRR – dB
100k
FREQUENCY - Hz
TPC 15. Closed-Loop Gain vs. Frequency
OPEN-LOOP GAIN – dB
COMMON-MODE REJECTION – dB
140
10k
PHASE – Degrees
10
80
+PSRR
60
–PSRR
40
35
30
NEGATIVE
EDGE
25
20
POSITIVE
EDGE
15
20
10
0
5
–20
10
100
1k
10k
FREQUENCY – Hz
100k
0
1M
TPC 14. Power Supply Rejection vs. Frequency
0
100
200
300
LOAD CAPACITANCE –pF
400
500
TPC 17. Small Signal Overshoot vs. Load Capacitance
–6–
REV. E
SSM2135
50
40
VS = 5V
TA = 25ⴗC
45
VS = 5V
AV = +1
RL = 10k⍀
f = 1kHz
THD+N = 1%
TA = 25ⴗC
35
IMPEDANCE – ⍀
35
OUTPUT VOLTAGE – V
40
AVCL = +100
30
25
AVCL = +10
20
15
30
25
20
15
10
10
5
5
AVCL = +1
100
1k
10k
FREQUENCY – Hz
100k
0
1M
0
TPC 18. Output Impedance vs. Frequency
35
40
2.0
VS = 5.0V
POSITIVE OUTPUT SWING – V
MAXIMUM OUTPUT – V
30
5.0
VS = 5V
TA = 25ⴗC
AV = +1
f = 1kHz
THD+N = 1%
4
3
2
1
1.5
4.5
+SWING
RL = 2k⍀
4.0
1.0
+SWING
RL = 600⍀
+SWING
RL = 2k⍀
0.5
3.5
+SWING
RL = 600⍀
1
10
100
1k
LOAD RESISTANCE – ⍀
10k
3.0
–75
100k
TPC 19. Maximum Output Voltage vs. Load Resistance
–50
–25
0
25
50
TEMPERATURE – ⴗC
75
100
0
125
TPC 22. Output Swing vs. Temperature and Load
6
2.0
VS = 5V
RL = 2k⍀
TA = 25ⴗC
AV = +1
5
VS = 5V
0.5V VOUT
4.0V
1.5
SLEW RATE – V/␮S
MAXIMUM OUTPUT SWING – V
15
20
25
SUPPLY VOLTAGE – V
TPC 21. Output Swing vs. Supply Voltage
5
0
10
5
4
3
2
+SLEW RATE
1.0
–SLEW RATE
0.5
1
0
1k
10k
100k
FREQUENCY – Hz
1M
0
–75
10M
TPC 20. Maximum Output Swing vs. Frequency
REV. E
NEGATIVE OUTPUT SWING – V
0
10
–50
–25
0
25
50
TEMPERATURE – ⴗC
75
100
TPC 23. Slew Rate vs. Temperature
–7–
125
SSM2135
5
20
VS = 5.0V
TO = 3.9V
18
4
SUPPLY CURRENT – mA
OPEN-LOOP GAIN – V/␮V
16
RL = 2k⍀
14
12
10
RL = 600⍀
8
6
VS = ⴞ18V
VS = ⴞ15V
3
VS = +5.0V
2
1
4
2
0
–75
–50
–25
0
25
50
TEMPERATURE – ⴗC
75
0
–75
125
100
–25
0
25
50
TEMPERATURE – ⴗC
75
100
125
TPC 26. Supply Current vs. Temperature
TPC 24. Open-Loop Gain vs. Temperature
500
5
70
–50
GBW
60
3
␪m
55
50
–75
2
400
INPUT BIAS CURRENT – nA
4
65
GAIN-BANDWIDTH PRODUCT – MHz
PHASE MARGIN – Degrees
VS = 5V
–25
0
25
50
TEMPERATURE – ⴗC
75
100
VS = ⴞ15V
200
100
1
–50
VS = +5.0V
300
0
–75
125
–50
–25
0
25
50
TEMPERATURE – ⴗC
75
100
125
TPC 27. Input Bias Current vs. Temperature
TPC 25. Gain Bandwidth Product and Phase Margin
vs. Temperature
The SSM2135 is fully protected from phase reversal for inputs
going to the negative supply rail. However, internal ESD protection diodes will 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 W or higher series input resistor will prevent
phase inversion even with the input pulled 1 V below the negative supply.
APPLICATION INFORMATION
The SSM2135 is a low voltage audio amplifier that has exceptionally low noise and excellent sonic quality even when driving
loads as small as 25 W. Designed for single supply use, the
SSM2135’s inputs common-mode and output swing to 0 V.
Thus with a supply voltage at 5 V, both the input and output
will 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.
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.
“Hot” plugging the input to a signal generally does not present a
problem for the SSM2135, assuming the signal does not have
any voltage exceeding the device’s supply voltage. 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.
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 W with low distortion.
–8–
REV. E
SSM2135
APPLICATION CIRCUITS
Low Noise Microphone Preamplifier
Low Noise Stereo Headphone Driver Amplifier
Figure 1 shows the SSM2135 used in a stereo headphone driver
for multimedia applications with the AD1848, a 16-bit stereo
codec. The SSM2135 is equally well suited for the serial-bused
AD1849 stereo codec. The headphone’s impedance can be as
low as 25 W, 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.
The SSM2135’s 4.7 nV/÷Hz input noise in conjunction with
low distortion makes it an ideal device for amplifying low level
signals such as those produced by microphones. Figure 3 illustrates a stereo microphone input circuit feeding a multimedia
sound codec. As shown, the gain is set at 100 (40 dB), although
it can be set to other gains depending on the microphone output
levels. Figure 4 shows the preamplifier’s harmonic distortion
performance with 1 V rms output while operating from a single
5 V supply.
LOUT
VCC
GND
VREF
10k⍀
40
35/36
8.66k⍀
2
+5V
0.1␮F
1
1/2
SSM2135
10␮F
3
34/37
470␮F
L CH.
32
0.1␮F
10k⍀
10␮F
R CH.
5
AD1848
8 0.1␮F
6
4
ROUT
The SSM2135 is biased to 2.25 V by the VREF pin of the AD1848
codec. The same voltage is buffered by the 2N4124 transistor to
provide “phantom power” to the microphone. A typical electret
condenser microphone with an impedance range of 100 W to 1 kW
works well with the circuit. This power booster circuit may be
omitted for dynamic microphone elements.
7
1/2
470␮F
SSM2135
+5V 10␮F
AGND
41
10␮F
2k⍀
10k⍀
8.66k⍀
2
3
10k⍀
+5V
8
1
1/2
+5V
4 SSM2135
0.1␮F
2N4124
Figure 1. A Stereo Headphone Driver for Multimedia
Sound Codec
R CHANNEL
MIC IN
29
35/36
34/37
32
10␮F
Figure 2 shows the total harmonic distortion characteristics
versus frequency driving into a 32 W 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 mF bypass is recommended.
AUDIO PRECISION
1
100⍀
L CHANNEL
MIC IN
10k⍀
2k⍀
10␮F
LMIC
VCC
GND
VREF
0.1␮F
AD1848
5
6
100⍀
7
1/2
SSM2135
28
RMIC
10k⍀
Figure 3. Low Noise Microphone Preamp for Multimedia
Sound Codec
AUDIO PRECISION
1
THD+(%) VS FREQ(Hz)
THD+(%) VS FREQ(Hz)
0.1
0.1
0.010
0.001
0.010
20
0.0005
20
100
1k
10k
20k
1k
10k
20k
Figure 4. MIC Preamp THD+N Performance (VS = 5 V,
AV = 40 dB, VOUT = 1 V rms, with 80 kHz Low-Pass Filter)
Figure 2. Headphone Driver THD+N vs. Frequency into a
32 W Load (VS = 5 V, with 80 kHz Low-Pass Filter)
REV. E
100
–9–
SSM2135
5V SUPPLY
AD1868
18-BIT
DAC
VL
VBL
DL
18-BIT
LL SERIAL
REG.
9.76k⍀
7.68k⍀
VREF
1/2
SSM2135
VOL
330pF
7.68k⍀
AGND
18-BIT
LR SERIAL
REG.
DGND
LEFT
CHANNEL
OUTPUT
47k⍀
100pF
CK
DR
220␮F
VREF
7.68k⍀
VOR
18-BIT
DAC
VS
100pF
9.76k⍀
7.68k⍀
VBR
1/2
SSM2135
330pF
220␮F
RIGHT
CHANNEL
OUTPUT
47k⍀
Figure 5. 5 V Stereo 18-Bit DAC
18-Bit Stereo CD-DAC Output Amplifier
Single-Supply Differential Line Receiver
The SSM2135 makes an ideal single-supply stereo output
amplifier for audio D/A converters because of its low noise and
distortion. Figure 5 shows the implementation of an 18-bit
stereo DAC channel. The output amplifier also provides low-pass
filtering for smoothing the oversampled audio signal. The filter’s
cutoff frequency is set at 22.5 kHz and has a maximally flat
response from dc to 20 kHz.
Receiving a differential signal with minimum distortion is achieved
using the circuit in Figure 7. 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 kW 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 kW precision resistor network.
As mentioned above, the amplifier’s outputs can drive directly
into a stereo headphone that has impedance as low as 25 W with
no additional buffering required.
10k⍀
+5V 10␮F+0.1␮F
Single Supply Differential Line Driver
Signal distribution and routing is often required in audio systems,
particularly portable digital audio equipment for professional
applications. Figure 6 shows a single supply line driver circuit
that has differential output. The bottom amplifier provides a 2 V
dc bias for the differential amplifier in order 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 W line termination at a reduced output amplitude.
20k⍀
1/2
SSM2135
20k⍀
DIFFERENTIAL
AUDIO IN
20k⍀
10⍀
1/2
SSM2135
2.0V
+5V
1␮F
100⍀
1k⍀
1/2
SSM2135
10␮F
AUDIO
OUT
7.5k⍀
+5V
5k⍀
+5V 10␮F+0.1␮F
0.1␮F
2.5k⍀
1/2
SSM2135
100␮F
AUDIO IN
Figure 7. Single-Supply Balanced Differential
Line Receiver
DIFFERENTIAL
AUDIO OUT
1k⍀
Pseudo-Reference Voltage Generator
1k⍀
10k⍀
1/2
SSM2135
2.0V
2.5k⍀
+5V
0.1␮F
100⍀
1␮F
+5V
1/2
SSM2135
7.5k⍀
5k⍀
Figure 6. Single-Supply Differential Line Driver
For single-supply circuits, a reference voltage source is often
required for biasing purposes or signal offsetting purposes. The
circuit in Figure 8 provides a supply splitter function with low
output impedance. The 1 mF 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 mF feedback
capacitor compensates the amplifier in the presence of a heavy
capacitive load, maintaining stability.
The output can source or sink up to 12 mA of current with a
5 V supply, limited only by the 100 W output resistor. Reducing
the resistance will increase the output current capability.
Alternatively, increasing the supply voltage to 12 V also
improves the output drive to more than 25 mA.
–10–
REV. E
SSM2135
Logarithmic Volume Control Circuit
VS+ = 5V Æ 12V
Figure 10 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.
R3
2.5k⍀
C1
0.1␮F
R1
5k⍀
R4
100k⍀
1/2
SSM2135
+5V
0.1␮F
VS+
OUTPUT
2
C2
1␮F
R2
5k⍀
+5V 10␮F+0.1␮F
3
47␮F
L AUDIO
IN
Figure 8. Pseudo-Reference Generator
14
DGND
VIN
VDD
FB
1
OUTA
AD7111
AGND
Digital Volume Control Circuit
10
Working in conjunction with the AD7528/PM7528 dual 8-bit
D/A converter, the SSM2135 makes an efficient audio attenuator,
as shown in Figure 9. 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 DACs’ internal R-2R ladder switches operating properly. This voltage is also the optimal midpoint of the SSM2135’s
common-mode and output swing range. With the circuit as
shown, 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.
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.
1/2
SSM2135
47␮F
L AUDIO
OUT
2
+5V
0.1␮F
3
47␮F
R AUDIO
IN
DGND
VIN
14
VDD
FB
1
OUTA
AD7111
AGND
DATA IN
AND
CONTROL
10
1/2
SSM2135
47␮F
2
R AUDIO
OUT
2k
10
+5V
+5V
0.1␮F
100⍀
2.0V
1/2
SSM2135
7.5k
2.0V
1␮F
5k
Figure 10. Single-Supply Logarithmic Volume Control
AD7528/PM7528
3
+5V 10␮F+0.1␮F
FB
REFA
OUTA
DAC A
L AUDIO
IN
2
1/2
SSM2135
47␮F
L AUDIO
OUT
DATA IN
6
CONTROL
SIGNAL
R AUDIO
IN
DACA/
DACB
15
CS
16
WR
18
19
FB
REFB
OUTB
DACB
20
1
1/2
SSM2135
47␮F
R AUDIO
OUT
2k⍀
VDD
DGND
17
0.1␮F
+5V
5
+5V
0.1␮F
100⍀
2.0V
1/2
SSM2135
+5V
7.5k⍀
2.0V
1␮F
5k⍀
Figure 9. Digital Volume Control
REV. E
–11–
SSM2135
SPICE MACROMODEL
*SSM2135 SPICE Macro-Model
9/92, Rev. A
*
JCB/ADI
*Copyright 1993 by Analog Devices, Inc.
*
*Node Assignments
*
*
Noninverting Input
*
Inverting Input
*
Positive Supply
*
Negative Supply
*
Output
.SUBCKT SSM2135
3
2
7
4
6
*
* INPUT STAGE
R3
4
19 1.5E3
R4
4
20 1.5E3
C1
19 20 5.311E–12
I1
7
18 106E–6
IOS
2
3
25E–09
EOS 12 5
POLY(1) 51 4
25E–06 1
Q1
19 3
18
PNP1
Q2
20 12 18
PNP1
CIN 3
2
3E–12
D1
3
1
DY
D2
2
1
DY
EN
5
2
22
0
1
GN1 0
2
25
0
1E–5
GN2 0
3
28
0
1E–5
*
* VOLTAGE NOISE SOURCE WITH FLICKER NOISE
DN1 21 22 DEN
DN2 22 23 DEN
VN1 21 0
DC 2
VN2 0
23 DC 2
*
* CURRENT NOISE SOURCE WITH FLICKER NOISE
DN3 24 25 DIN
DN4 25 26 DIN
VN3 24 0
DC 2
VN4 0
26 DC 2
*
* SECOND CURRENT NOISE SOURCE
DN5 27 28 DIN
DN6 28 29 DIN
VN5 27 0
DC 2
VN6 0
29 DC 2
*
* GAIN STAGE & DOMINANT POLE AT .2000E+01 HZ
G2
34 36 19
20 2.65E–04
R7
34 36 39E+06
V3
35 4
DC
6
D4
36 35 DX
VB2 34 4
1.6
*
* SUPPLY/2 GENERATOR
ISY
7
4
0.2E–3
R10 7
60 40E+3
R11 60 4
40E+3
C3
60 0
1E–9
*
* CMRR STAGE & POLE AT 6 kHZ
ECM
50 4
POLY(2) 3 60 2 60 0 1.6 1.6
CCM 50 51 26.5E–12
RCM1 50 51 1E6
RCM2 51 4
1
*
*
OUTPUT STAGE
R12 37 36 1E3
R13 38 36 500
C4 37 6 20E–12
C5 38 39 20E–12
M1 39 36 4 4 MN L=9E–6 W=1000E–6 AD=15E–9 AS=15E–9
M2 45 36 4 4 MN L=9E–6 W=1000E–6 AD=15E–9 AS=15E–9
5
39 47 DX
D6 47 45 DX
Q3 39 40 41 QPA 8
VB 7 40 DC 0.861
R14 7 41 375
Q4 41 7 43 QNA 1
R17 7 43 15
Q5 43 39 6
QNA 20
Q6 46 45 6
QPA 20
R18 46 4 15
Q7 36 46 4
QNA 1
M3 6 36 4 4 MN L=9E–6 W=2000E–6 AD=30E–9 AS=30E–9
*
* NONLINEAR MODELS USED
*
.MODEL DX D (IS=1E–15)
.MODEL DY D (IS=1E–15 BV=7)
.MODEL PNP1 PNP (BF=220)
.MODEL DEN D(IS=1E–12 RS=1016 KF=3.278E–15 AF=1)
.MODEL DIN D(IS=1E–12 RS=100019 KF=4.173E–15 AF=1)
.MODEL QNA NPN(IS=1.19E–16 BF=253 VAF=193 VAR=15 RB=2.0E3
+ IRB=7.73E–6 RBM=132.8 RE=4 RC=209 CJE=2.1E–13 VJE=0.573
+ MJE =0.364 CJC=1.64E–13 VJC=0.534 MJC=0.5 CJS=1.37E–12
+ VJS=0.59 MJS=0.5 TF=0.43E–9 PTF=30)
.MODEL QPA PNP(IS=5.21E–17 BF=131 VAF=62 VAR=15 RB=1.52E3
+ IRB=1.67E 5–RBM=368.5 RE=6.31 RC=354.4 CJE=1.1E–13
+ VJE=0.745 MJE=0.33 CJC=2.37E–13 VJC=0.762 MJC=0.4
+ CJS=7.11E–13 VJS=0.45 MJS=0.412 TF=1.0E–9 PTF=30)
.MODEL MN NMOS(LEVEL=3 VTO=1.3 RS=0.3 RD=0.3 TOX=8.5E–8
+ LD=1.48E–6WD=1E–6 NSUB=1.53E16UO=650 DELTA= 10VMAX=2E5
+ XJ=1.75E–6 KAPPA=0.8 ETA=0.066 THETA=0.01TPG=1 CJ=2.9E–4
+ PB=0.837 MJ=0.407 CJSW=0.5E–9 MJSW=0.33)
*
.ENDS SSM-2135
–12–
REV. E
SSM2135
OUTLINE DIMENSIONS
8-Lead Standard Small Outline Package [SOIC]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
8
5
1
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
SEATING
0.10
PLANE
6.20 (0.2440)
5.80 (0.2284)
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.33 (0.0130)
0.50 (0.0196)
ⴛ 45ⴗ
0.25 (0.0099)
8ⴗ
0.25 (0.0098) 0ⴗ 1.27 (0.0500)
0.41 (0.0160)
0.19 (0.0075)
COMPLIANT TO JEDEC STANDARDS MS-012AA
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
REV. E
–13–
SSM2135
Revision History
Location
Page
2/03—Data Sheet changed from REV. D to REV. E.
Removed 8-Lead Plastic DIP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Universal
Edits to THERMAL CHARACTERISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Edits to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
–14–
REV. E
–15–
–16–
PRINTED IN U.S.A.
C00349–0–2/03(E)