SSM2165-2P AD [Analog Devices], SSM2165-2P Datasheet

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SSM2165-2P

Manufacturer Part Number
SSM2165-2P
Description
Microphone Preamplifier with Variable Compression and Noise Gating
Manufacturer
AD [Analog Devices]
Datasheet
a
GENERAL DESCRIPTION
The SSM2165 is a complete and flexible solution for condition-
ing 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 compres-
sion 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 amplifi-
cation 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
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.
REV. A
All signals are in rms volts or dBu (0 dBu = 0.775 V rms).
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 ( 1 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
1
, a VCA gain of 18 dB,
Variable Compression and Noise Gating
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
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 V), 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.
Figure 1a. SSM2165-1 Compression and Gating Characteristics
Figure 1b. SSM2165-2 Compression and Gating Characteristics
AUDIO
Microphone Preamplifier with
IN+
0.1 F
C1
–10
–20
–30
–40
–50
–60
–70
–10
–40
–50
–60
–20
–30
FUNCTIONAL BLOCK DIAGRAM
0
–80
0
–80
SSM2165
–70
–70
GND
V+
V+
+1
World Wide Web Site: http://www.analog.com
BUFFER
BUF
–60
–60
LEVEL
DETECTOR
OUT
INPUT – dBu
AVG CAP
INPUT – dBu
–50
–50
R
10 F
2
A
22 F
C2
+
C3
–40
–40
R
VCA
2
+
© Analog Devices, Inc., 1999
A
SSM2165*
25k
–30
–30
IN
CONTROL
R1
VCA
–20
–20
COMPRESSION
RATIO SET
–10
–10
V
OUT

Related parts for SSM2165-2P

SSM2165-2P Summary of contents

Page 1

... 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 – + 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 – ...

Page 2

... Input Voltage Range Output Voltage Range Gain Bandwidth Product SSM2165-1 SSM2165-2 CONTROL SECTION VCA Dynamic Gain Range VCA Fixed Gain SSM2165-1 SSM2165-2 Rotation Point SSM2165-1 SSM2165-2 Compression Ratio, Min Compression Ratio, Max Control Feedthrough POWER SUPPLY Supply Voltage Range Supply Current ...

Page 3

... JC ORDERING GUIDE Temperature Package Model Range Description SSM2165-1P – +85 C Plastic DIP SSM2165-2P – +85 C Plastic DIP SSM2165-1S – +85 C Narrow SOIC SSM2165-2S – +85 C Narrow SOIC 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 ...

Page 4

... SSM2165–1 0.1 SSM2165–2 0.050 20 100 1k FREQUENCY – Hz Figure 4. THD + N (%) vs. Frequency (Hz) SSM2165–2 10:1 15:1 COMP SSM2165– SSM2165–2 –10 – –30 –40 –50 –60 –70 20 10k 30k Figure 7. PSRR vs. Frequency, Referred to Input –4– ...

Page 5

... SSM2165-1 and V rp SSM2165-2 (see Figures 1a and 1b). The “nominal gain” of the system for the SSM2165-1, and 8 dB for the SSM2165-2. System gain is measured dB. Input signals below V approximately 1: result, the gain of the system is small ...

Page 6

... F Figure 11. Functional Block Diagram and Typical Voice Application The bandwidth of the SSM2165 is quite wide at all gain set- tings. The upper –3 dB point is approximately 300 kHz. The GBW plots are shown in Figure 6. While the noise of the input buffer is fixed, the input referred noise of the VCA is a function of gain ...

Page 7

... That is, in the limiting region change of input results change of output. The rotation point is set (–26 dBu) for the SSM2165-1 and 100 mV (–18 dBu) for the SSM2165-2. In the SSM2165, limiting is compression at a fixed compression ratio of approxi- mately 15:1 ...

Page 8

... This point is the noise gate threshold, and should be approximately 500 V (–64 dBu). The noise gate threshold on the SSM2165 is fixed at 500 V, a practical value for many microphones. Should you require a different noise gate threshold, consider using the SSM2166. ...

Page 9

... Power-down and mute functions are also built in. Custom- ized versions of the SSM2165 are available for large volume users. The wide dynamic range of the SSM2165 makes it useful in many applications other than microphone signal conditioning such as a sustain generator for guitars. For further information, contact your Analog Devices representative. – ...

Page 10

... SSM2165 0.0098 (0.25) 0.0040 (0.10) OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Plastic DIP (N-8) 0.430 (10.92) 0.348 (8.84 0.280 (7.11) 0.240 (6.10 0.325 (8.25) PIN 1 0.100 (2.54) 0.300 (7.62) BSC 0.060 (1.52) 0.210 0.015 (0.38) (5.33) MAX 0.130 0.160 (4.06) (3.30) MIN 0.115 (2.93) 0.015 (0.381) 0.022 (0.558) SEATING 0.070 (1.77) 0.008 (0.204) PLANE 0.014 (0.356) ...

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