ANALOG DEVICES SSM2167 Service Manual
Low Voltage Microphone Preamplifier with
G
www.BDTIC.com/ADI
Variable Compression and Noise Gating
FEATURES
Complete microphone conditioner in a 10-lead package
Single 3 V operation
Low shutdown current < 2 μA
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
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 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 10:1 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 background 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. 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 device is available in a 10-lead MSOP package, and is
guaranteed for operation over the extended industrial
temperature range of −40°C to +85°C.
SSM2167
PIN CONFIGURATION
GND
1
VCA
2
IN
SSM2167
SHUTDOWN
3
TOP VIEW
(Not to S cale)
4
BUF
OUT
INPUT
5
Figure 1. 10-Lead MSOP (RM Suffix)
(ROTATION POINT)
COMPRESSION
DOWNWARD
EXPANSION
THRESHOLD
(NOISE GATE)
OUTPUT (dB)
DOWNWARD
EXPANSION
REGION
Figure 2. General Input/Output Characteristics
REGION
1
V
DE
INPUT (dB)
V
10
DD
OUTPUT
9
8
COMPRESSION RATIO
7
GATE THRS
AVG CAP
6
LIMITIN
THRESHOLD
1
r
1
V
RP
LIMITING
REGION
VCA GAIN
2628-001
02628-002
Rev. C
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 registered trademarks are the 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 ©2001–2007 Analog Devices, Inc. All rights reserved.
SSM2167
www.BDTIC.com/ADI
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Pin Configuration ............................................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Absolute Maximum Ratings ............................................................ 4
Thermal Resistance ...................................................................... 4
ESD Caution .................................................................................. 4
Typical Performance Characteristics ............................................. 5
Applications Information ................................................................ 8
Theory of Operation .................................................................... 8
REVISION HISTORY
11/07—Rev. B to Rev. C
Updated Format .................................................................. Universal
Changes to PSRR .............................................................................. 3
Updated Outline Dimensions ....................................................... 11
Changes to Ordering Guide .......................................................... 11
9/03—Rev. A to Rev. B
Deleted SSM2167-2 Model ................................................ Universal
Changes to Ordering Guide ............................................................ 3
Edits to Figure 2 and Figure 3 ......................................................... 6
Updated Outline Dimensions ......................................................... 9
Signal Path ......................................................................................8
Level Detector ................................................................................9
Control Circuitry ...........................................................................9
Setting the Compression Ratio ....................................................9
Setting the Noise Gate Threshold
(Downward Expansion) ............................................................ 10
Rotation Point (Limiting) .......................................................... 10
Shutdown Feature ....................................................................... 10
PCB Layout Considerations ...................................................... 10
Outline Dimensions ....................................................................... 11
Ordering Guide .......................................................................... 11
3/02—Rev. 0 to Rev. A
Edits to Specifications ....................................................................... 2
Edits to Figure 2 and Figure 3 .......................................................... 6
7/01—Revision 0: Initial Version
Rev. C | Page 2 of 12
SSM2167
www.BDTIC.com/ADI
SPECIFICATIONS
VS = 3.0 V, f = 1 kHz, RL = 100 kΩ, R
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
AUDIO SIGNAL PATH
Voltage Noise Density en 10:1 compression 20 nV/√Hz
Noise 20 kHz bandwidth, VIN = GND −70 dBV
Total Harmonic Distortion + Noise THD + N VIN = 100 mV rms 0.2 %
Input Impedance Z
Output Impedance Z
Load Drive Minimum resistive load 5 kΩ
Maximum capacitive load 2 nF
Input Voltage Range 0.4% THD + N 600 mV rms
Output Voltage Range 0.4% THD + N 700 mV rms
Gain Bandwidth Product 1:1 compression, VCA G = 18 dB 1 MHz
CONTROL SECTION
VCA Dynamic Gain Range 40 dB
VCA Fixed Gain 18 dB
Compression Ratio, Minimum 1:1
Compression Ratio, Maximum See Table 4 for R
Rotation Point 63 mV rms
Noise Gate Range Maximum threshold −40 dBV
POWER SUPPLY
Supply Voltage V
Supply Current I
DC Output Voltage 1.4 V
Power Supply Rejection Ratio PSRR VSY = 2.5 V to 6 V 45 dB
SHUTDOWN
Supply Current I
= 0 Ω, TA = 25°C, VIN = 100 mV rms, R
COMP
100 kΩ
IN
145 Ω
OUT
2.5 5.5 V
SY
2.3 5 mA
SY
Pin 3 = GND 2 8 μA
SY
= 2 kΩ, unless otherwise noted.
GATE
10:1
COMP
Rev. C | Page 3 of 12
SSM2167
www.BDTIC.com/ADI
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Supply Voltage 6 V
Input Voltage 6 V
Operating Temperature Range −40°C to +85°C
Junction Temperature 150°C
Lead Temperature (Soldering, 10 sec) 300°C
883 (Human Body) Model 500 V
THERMAL RESISTANCE
θJA is specified for worst-case conditions, that is, θJA is specified
for device soldered in 4-layer circuit board for surface-mount
packages.
Table 3.
Package Type θJA θJC Unit
10-Lead MSOP (RM) 180 35 °C/W
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.
ESD CAUTION
Rev. C | Page 4 of 12
Loading...