Analog Devices SSM2165-2S, SSM2165-1S, SSM2165-1P Datasheet
Microphone Preamplifier with
VCA
+1
VCA
IN
BUF
OUT
V+
V+
+
C2
10F
BUFFER
LEVEL
DETECTOR
CONTROL
SSM2165
C1
0.1F
AUDIO
IN+
V
OUT
R1
25k⍀
C3
22F
AVG CAP
COMPRESSION
RATIO SET
GND
R
A
2
R
A
2
+
a
Variable Compression and Noise Gating
FEATURES
Complete Microphone Conditioner in an 8-Lead Package
Single 5 V Operation
Preset Noise Gate Threshold
Compression Ratio Set by External Resistor
Automatic Limiting Feature Prevents ADC Overload
Adjustable Release Time
Low Noise and Distortion
20 kHz Bandwidth (ⴞ1 dB)
Low Cost
APPLICATIONS
Microphone Preamplifier/Processor
Computer Sound Cards
Public Address/Paging Systems
Communication Headsets
Telephone Conferencing
Guitar Sustain Effects Generator
Computerized Voice Recognition
Surveillance Systems
Karaoke and DJ Mixers
GENERAL DESCRIPTION
The SSM2165 is a complete and flexible solution for conditioning microphone inputs in computer audio systems. It is also
excellent for improving vocal clarity in communications and
public address systems. A low noise voltage controlled amplifier
(VCA) provides a gain that is dynamically adjusted by a control
loop to maintain a set compression characteristic. The compression ratio is set by a single resistor and can be varied from 1:1 to
over 15:1 relative to the fixed rotation point. Signals above the
rotation point are limited to prevent overload and to eliminate
“popping.” A downward expander (noise gate) prevents amplification of noise or hum. This results in optimized signal levels
prior to digitization, thereby eliminating the need for additional
gain or attenuation in the digital domain that could add noise or
impair accuracy of speech recognition algorithms. The flexibility
of setting the compression ratio and the time constant of the
level detector, coupled with two values of rotation point, make
the SSM2165 easy to integrate in a wide variety of microphone
conditioning applications.
The SSM2165 is an ideal companion product for audio codecs
used in computer systems, such as the AD1845 and AD1847.
The device is available in 8-lead SOIC and P-DIP packages, and
guaranteed for operation over the extended industrial temperature
range of –40°C to +85°C. As shown in Figure 1a, the SSM2165-1
has a rotation point of –25.7 dBu (40 mV)
and gives –7.7 dBu (320 mV) before limiting. As shown in Figure
1b, the SSM2165-2 has a rotation point of –17.8 dBu (100 mV),
*Patents pending.
1
REV. B
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.
All signals are in rms volts or dBu (0 dBu = 0.775 V rms).
1
, a VCA gain of 18 dB,
SSM2165*
FUNCTIONAL BLOCK DIAGRAM
a VCA gain of 8 dB and gives –9.8 dBu (250 mV) before limiting.
Both have a noise gate threshold of –64 dBu (500 µV), below
which downward expansion reduces the gain with a ratio of
approximately 1:3. That is, a –3 dB reduction of output signal
occurs with a –1 dB reduction of input signal. For applications
requiring adjustable noise gate threshold, VCA gain up to 18 dB,
and adjustable rotation point, please refer to the SSM2166.
0
–10
–20
–30
–40
OUTPUT – dBu
–50
–60
INPUT – dBu
Figure 1a. SSM2165-1 Compression and Gating Characteristics
0
–10
–20
–30
–40
OUTPUT – dBu
–50
–60
–70
INPUT – dBu
Figure 1b. SSM2165-2 Compression and Gating Characteristics
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 © Analog Devices, Inc., 2002
–10–80 –70 –60 –50 –40 –30 –20
–10–80 –70 –60 –50 –40 –30 –20
SSM2165–SPECIFICATIONS
(V+ = 5 V, f = 1 kHz, RL = 100 k⍀, R
= 0 ⍀, TA = 25ⴗC, unless otherwise noted)
COMP
Parameter Symbol Conditions Min Typ Max Unit
AUDIO SIGNAL PATH
Voltage Noise Density
e
n
15:1 Compression, V
= GND 17 nV/√Hz
IN
Noise 20 kHz Bandwidth, VIN = GND –109 dBu
2
1
Total Harmonic Distortion THD+N
SSM2165-1 2nd and 3rd Harmonics, V
SSM2165-2 2nd and 3rd Harmonics, V
= –30 dBu 0.2 0.5 %
IN
= –20 dBu 0.2 0.5 %
IN
22 kHz Low-Pass Filter
Input Impedance Z
Output Impedance Z
IN
OUT
180 kΩ
75 Ω
Load Drive Resistive 5 kΩ
Capacitive 2 nF
Input Voltage Range 1% THD 1 V rms
Output Voltage Range 1% THD 1.4 V rms
Gain Bandwidth Product 1:1 Compression
SSM2165-1 VCA G = 18 dB 300 kHz
SSM2165-2 VCA G = 8 dB 100 kHz
CONTROL SECTION
VCA Dynamic Gain Range 40 dB
VCA Fixed Gain
SSM2165-1 18 dB
SSM2165-2 8dB
Rotation Point
SSM2165-1 40 mV rms
SSM2165-2 100 mV rms
Compression Ratio, Min 1:1
Compression Ratio, Max 15:1
Control Feedthrough 15:1 Compression ±5mV
POWER SUPPLY
Supply Voltage Range V
Supply Current I
S
SY
4.5 5.5 V
7.5 10 mA
Quiescent Output Voltage Level 2.2 V
Power Supply Rejection Ratio2PSRR 50 dB
NOTES
1
0 dBu = 0.775 V rms.
2
Referred to input.
Specifications subject to change without notice.
–2–
REV. B
SSM2165
WARNING!
ESD SENSITIVE DEVICE
ABSOLUTE MAXIMUM RATINGS
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 V
Audio Input Voltage . . . . . . . . . . . . . . . . . . . . .Supply Voltage
Operating Temperature Range . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature (T
) . . . . . . . . . . . . . . . . . . . . . . . 150°C
J
Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . . . 300°C
ESD RATINGS
883 (Human Body) Model . . . . . . . . . . . . . . . . . . . . . . . 2.0 kV
THERMAL CHARACTERISTICS
Thermal Resistance
8-Lead Plastic DIP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103°C/W
θ
JA
θ
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43°C/W
JC
8-Lead SOIC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158°C/W
θ
JA
θ
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43°C/W
JC
ORDERING GUIDE
Temperature Package Package
Model Range Description Options
SSM2165-1P* –40°C to +85°C Plastic DIP N-8
SSM2165-1S –40°C to +85°C Narrow SOIC SO-8
SSM2165-2S –40°C to +85°C Narrow SOIC SO-8
*Not for new design, obsolete April 2002.
PIN CONFIGURATION
GND
VCA
BUF
OUT
AUDIO +IN
1
2
IN
3
4
SSM2165
TOP VIEW
(Not to Scale)
8
V+
7
OUTPUT
6
COMP RATIO SET
5
AVG CAP
PIN FUNCTION DESCRIPTIONS
Pin # Mnemonic Function
1 GND Ground
2 VCA
IN
VCA Input Pin. A typical
connection is a 1 µF–10 µF
capacitor from the buffer output
pin (Pin 3) to this pin.
3 BUF
OUT
Input Buffer Amplifier Output
Pin. Must not be loaded by
capacitance to ground.
4 AUDIO +IN Input Audio Signal. The input
signal should be ac-coupled
(0.1 µF typical) into this pin.
5 AVG CAP Detector Averaging Capacitor.
A capacitor, 2.2 µF–22 µF, to
ground from this pin is the
averaging capacitor for the
detector circuit.
6 COMP RATIO SET Compression Ratio Set Pin. A
resistor to ground from this pin
sets the compression ratio as
shown in TPC 1.
7 OUTPUT Output Signal.
8 V+ Positive Supply, 5 V Nominal.
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 SSM2165 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. B
–3–
SSM2165
260
240
220
200
180
160
140
– k⍀
120
COMP
R
100
80
60
40
20
0
1:1 15:12:1 5:1 10:1
TPC 1. Compression Ratio vs. R
–Typical Performance Characteristics
TA ⴝ 25ⴗC
ⴝ 5V
V
S
ⴝ 100k⍀
R
L
SSM2165–1
SSM2165–2
COMPRESSION RATIO
COMP
5V
100
90
TA ⴝ 25ⴗC
10
0%
COMPRESSION RATIO ⴝ 15:1
NOISE BW ⴝ 20kHz
1s
TPC 4. Wideband Output Noise
5
TA ⴝ 25ⴗC
COMP RATIO ⴝ 1:1
ⴝ 100k⍀/10k⍀
R
L
ⴝ 5V
V
S
1
THDⴙN – %
0.1
0.050
0.01 1
INPUT – V rms
SSM2165–1
SSM2165–2
0.1
TPC 2. THD + N (%) vs. Input (V rms)
5
TA ⴝ 25ⴗC
ⴝ 5V
V
S
COMP RATIO ⴝ 1:1
ⴝ –20dBu (–1)
V
IN
ⴝ –30dBu (–2)
V
IN
ⴝ 100k⍀
R
L
1
THDⴙN – %
SSM2165–1
0.1
0.050
20 30k100
SSM2165–2
1k 10k
FREQUENCY – Hz
TPC 3. THD + N (%) vs. Frequency (Hz)
70
60
50
40
30
G = 18dB
20
GAIN – dB
G = 8dB
10
0
–10
–20
1k 1M10k 100k
COMP RATIO ⴝ 15:1
R
COMP
ⴝ 40V rms
V
IN
FREQUENCY – Hz
ⴝ 0
TPC 5. GBW Curves vs. VCA Gain
–30
–40
–50
PSRR – dB
–60
–70
20 30k100 1k
V+ ⴝ 5ⴞ1V p-p
10k
FREQUENCY – Hz
TPC 6. PSRR vs. Frequency, Referred to Input
–4–
REV. B
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