ssm2166p Analog Devices, Inc., ssm2166p Datasheet

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ssm2166p

Manufacturer Part Number
ssm2166p
Description
Microphone Preamplifier With Variable Compression And Noise Gating
Manufacturer
Analog Devices, Inc.
Datasheet
GENERAL DESCRIPTION
The SSM2166 integrates 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 a user defined “rotation point”;
signals above the rotation point are limited to prevent overload
and eliminate “popping.” In the 1:1 compression setting, the
SSM2166 can be programmed with a fixed gain of up to 20 dB;
*Patents pending.
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. Trademarks and
registered trademarks are the property of their respective companies.
FEATURES
Complete Microphone Conditioner in a 14-Lead Package
Single +5 V Operation
Adjustable Noise Gate Threshold
Compression Ratio Set by External Resistor
Automatic Limiting Feature—Prevents ADC Overload
Adjustable Release Time
Low Noise and Distortion
Power-Down Feature
20 kHz Bandwidth ( 1 dB)
Low Cost
APPLICATIONS
Microphone Preamplifier/Processors
Computer Sound Cards
Public Address/Paging Systems
Communication Headsets
Telephone Conferencing
Guitar Sustain Effects Generators
Computerized Voice Recognition
Surveillance Systems
Karaoke and DJ Mixers
+
R2 = 10k
1 F
AUDIO
Figure 2. Functional Block Diagram and Typical Speech Application
+IN
–IN
0.1 F
R1 = 10k
POWER
6
7
DOWN
SSM2166
12
BUFFER
BUFOUT
1
GND
Variable Compression and Noise Gating
DETECTOR
5
LEVEL
AVG
CAP
10 F
VCA
+
22 F
3
IN
8
4
1k
this gain is in addition to the variable gain in other compression
settings. The input buffer can also be configured for front-end
gains of 0 dB to 20 dB. A downward expander (noise gate)
prevents amplification of noise or hum. This results in opti-
mized 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 compression ratio and time constants are set
externally. A high degree of flexibility is provided by the VCA
Gain, Rotation Point, and Noise Gate adjustment pins.
The SSM2166 is an ideal companion product for audio codecs
used in computer systems, such as the AD1845 and AD1847.
The device is available in a 14-lead SOIC package, and is guar-
anteed for operation over the extended industrial temperature
range of –40°C to +85°C. For similar features and performance
in an 8-lead package, please refer to the SSM2165.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
+
10 F
1k
VCA
+
25k
Figure 1. SSM2166 Compression and Gating Char-
acteristics with 10 dB of Fixed Gain (The Gain Adjust
Pin Can Be Used to Vary This Fixed Gain Amount)
Microphone Preamplifier with
10
VCA
CONTROL
*
R
–10
–20
–30
–40
–50
–60
COMPRESSION
RATIO
SET
10
0
–70
V+
14
–60
RATIO = 10:1
*
OPTIONAL
13
2
OUTPUT
9
11
RATIO = 1:1
RATIO = 2:1
© 2003 Analog Devices, Inc. All rights reserved.
VCA GAIN
NOISE GATE
–50
POINT SET
2.3k
ROTATION
ADJ
500k
17k
SET
–40
INPUT – dBu
–30
V+
SSM2166
–20
www.analog.com
–10
0
*

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ssm2166p Summary of contents

Page 1

... INPUT – dBu VCA GAIN ADJ 13 OUTPUT 500k 9 NOISE GATE SET 17k 11 ROTATION POINT SET COMPRESSION RATIO SET * OPTIONAL © 2003 Analog Devices, Inc. All rights reserved. * –10 0 www.analog.com ...

Page 2

SSM2166–SPECIFICATIONS Parameter AUDIO SIGNAL PATH Voltage Noise Density Noise Total Harmonic Distortion Input Impedance Output Impedance Load Drive Buffer Input Voltage Range Output Voltage Range VCA Input Voltage Range Output Voltage Range Gain Bandwidth Product CONTROL SECTION VCA Dynamic Gain ...

Page 3

Pin No. Mnemonic 1 GND 2 GAIN ADJUST 3 VCA IN 4 VCA R 5 BUF OUT 6 –IN 7 AUDIO +IN 8 AVG CAP 9 NOISE GATE SET 10 COMP RATIO SET 11 ROTATION SET 12 POWER DOWN 13 ...

Page 4

SSM2166–Typical Performance Characteristics 0 COMP RATIO = 15:1 COMP RATIO = 10:1 COMP RATIO = 5:1 –10 –20 –30 – +25 – 300mV rms @ 1kHz IN – 100k L ...

Page 5

T = +25° 100k L COMPRESSION RATIO = 1:1 NOISE GATE SETTING GAIN ADJUST (PIN 2) = 1.25k 0.1 0. ...

Page 6

SSM2166 APPLICATION INFORMATION The SSM2166 is a complete microphone signal conditioning system on a single integrated circuit. Designed primarily for voice-band applications, this integrated circuit provides amplifi- cation, rms detection, limiting, variable compression, and downward expansion. An integral voltage-controlled amplifier ...

Page 7

R1 = 10k 6 –IN 7 AUDIO +IN 0 10k + 1 F Figure 4. Functional Block Diagram and Typical Application bandwidth is unaffected). The GBW plots are shown in TPC 8b. The lower 3 dB cutoff ...

Page 8

SSM2166 100mV 100 Figure 5b. RMS Level Detector Performance = 22 µ F with C AVG Control Circuitry The output of the rms level detector is a signal proportional to the log of the true rms value ...

Page 9

V DE INPUT – dB Figure 8. Effect of Varying the VCA Gain Setting The gain of the VCA can be reduced below making smaller than 1 kΩ. Switching Pin 2 through 330 Ω ...

Page 10

SSM2166 (4) When using high impedance sources (≥5 kΩ), system gains in excess are not recommended. This configuration is rarely appropriate, as virtually all high impedance inputs provide larger amplitude signals that do not require as much ...

Page 11

Figure 13a. Evaluation Board Topside Silkscreen (Not to Scale) Figure 13b. Evaluation Board Topside Metallization (Not to Scale) REV. B Figure 13c. Evaluation Board Backside Metallization (Not to Scale) Signal sources are connected to the SSM2166 through a 1/8" phone ...

Page 12

SSM2166 As a result, the output dc level of the buffer will match the output dc level of the SSM2166, which is approximately 2 blocking capacitor may be inserted on Pins 6 and 7. An evaluation board ...

Page 13

STEP 5. Adjusting the Rotation Point Set the input level to 15 mV, and observe the output on the oscilloscope. Adjust R3—ROTATION PT ADJ CW until the output level just begins to drop, then reverse so that the output is ...

Page 14

... C3 +V Bypass 2.2 µF–22 µF C4 Avg. Cap 0.01 µF C5 Mute Click Suppress 10 µF C6 Coupling 10 µF C7 VCA Noise/DC Balance IC1 SSM2166P Mic Preamp IC2 OP113FP Op Amp, Output Buffer S1 SPST Mute J1 1/8" Mini Phone Plug MIC Input J2 RCA Female Output Jack –14– REV. B ...

Page 15

COPLANARITY REV. B OUTLINE DIMENSIONS 14-Lead Standard Small Outline Package [SOIC] Narrow Body (R-14) Dimensions shown in millimeters and (inches) 8.75 (0.3445) 8.55 (0.3366 6.20 (0.2441) 5.80 (0.2283 ...

Page 16

SSM2166 Revision History Location 3/03—Data Sheet changed from REV REV. B. Deleted Plastic DIP package . . . . . . . . . . . . . . . . . . . . . . . ...

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