a
FEATURES
Complete Microphone Conditioner in a 10-Lead Package
Single 3 V Operation
Low Shutdown Current < 2 A
Adjustable Noise Gate Threshold
Adjustable Compression Ratio
Automatic Limiting Feature Prevents ADC Overload
Low Noise and Distortion: 0.2% THD + N
20 kHz Bandwidth
APPLICATIONS
Desktop, Portable, or Palmtop Computers
Telephone Conferencing
Communication Headsets
Two-Way Communications
Surveillance Systems
Karaoke and DJ Mixers
Low Voltage Microphone
Preamplifier with Variable
Compression and Noise Gating
SSM2167
PIN CONFIGURATION
10-Lead MSOP
(RM Suffix)
GND
VCA
IN
SHUTDOWN
BUF OUT
INPUT
1
2
3
4
5
10
V
DD
OUTPUT
COMPRESSION RATIO
GATE THRS
AVG CAP
SSM2167
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GENERAL DESCRIPTION
The SSM2167 is a complete and flexible solution for conditioning
microphone inputs in personal electronics and computer audio
systems. It is also excellent for improving vocal clarity in communi-
cations 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 10:1 relative to the fixed rotation point. Signals above
the rotation point are limited to prevent overload and to eliminate
鈥減opping.鈥?A downward expander (noise gate) prevents amplifica-
tion of background noise or hum. This results in optimized signal
levels prior to digitization, thereby eliminating the need for addi-
tional gain or attenuation in the digital domain. The flexibility of
setting the compression ratio and the time constant of the level
detector, coupled with two values of rotation point, make the
SSM2167 easy to integrate in a wide variety of microphone
conditioning applications.
The SSM2167 is available in two versions, with different amounts
of fixed gain. The SSM2167-1 has 18 dB of fixed gain, while
the SSM2167-2 features only 8 dB of fixed gain.
The device is available in 10-lead MSOP package, and guaranteed
for operation over the extended industrial temperature range of
鈥?0擄C to +85擄C.
LIMITING
THRESHOLD
(ROTATION POINT)
DOWNWARD COMPRESSION
REGION
EXPANSION
THRESHOLD
1
(NOISE GATE)
r
LIMITING
REGION
VCA GAIN
OUTPUT 鈥?dB
DOWNWARD
EXPANSION
REGION
1
1
V
DE
INPUT 鈥?dB
V
RP
Figure 1. General Input/Output Characteristics
REV. A
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.
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
漏 Analog Devices, Inc., 2002
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