Microphone Preamplifier with Variable Compression and Noise Gating Data Sheet SSM2166 and to eliminate popping. In the 1:1 compression setting, the FEATURES SSM2166 can be programmed with a fixed gain of up to 20 dB Complete microphone conditioner in a 14-lead SOIC package this gain is in addition to the variable gain in other compression Single 5 V operation settings. The input buffer can also be configured for front-end Adjustable noise gate threshold gains of 0 dB to 20 dB. A downward expander (noise gate) prevents Compression ratio set by external resistor amplification of noise or hum. This results in optimized signal Automatic limiting featureprevents ADC overload levels prior to digitization, thereby eliminating the need for Adjustable release time additional gain or attenuation in the digital domain that may Low noise and distortion add noise or impair accuracy of speech recognition algorithms. Power-down feature The compression ratio and time constants are set externally. A 20 kHz bandwidth (1 dB) high degree of flexibility is provided by the VCA gain, rotation APPLICATIONS point, and noise gate adjustment pins. Microphone preamplifiers/processors The SSM2166 is an ideal companion product for audio codecs Computer sound cards used in computer systems. The SSM2166 is available in a 14-lead Public address/paging systems SOIC package and is guaranteed for operation over the Communication headsets extended industrial temperature range of 40C to +85C. Telephone conferencing 10 Guitar sustain effects generators COMP RATIO = 10:1 0 Computerized voice recognition Surveillance systems 10 COMP RATIO = 2:1 Karaoke and DJ mixers 20 GENERAL DESCRIPTION COMP RATIO = 1:1 The SSM2166 integrates a complete and flexible solution for 30 conditioning microphone inputs in computer audio systems. It 40 is also excellent for improving vocal clarity in communications and public address systems. A low noise, voltage-controlled 50 amplifier (VCA) provides a gain that is dynamically adjusted by 60 a control loop to maintain a set compression characteristic. The 70 60 50 40 30 20 10 0 compression ratio is set by a single resistor and can be varied INPUT (dBu) from 1:1 to over 15:1 relative to a user-defined rotation point Figure 1. Compression and Gating Characteristics with 10 dB of Fixed Gain (The Gain Adjust Pin Can Be Used to Vary This Fixed Gain Amount) signals above the rotation point are limited to prevent overload FUNCTIONAL BLOCK DIAGRAM AND TYPICAL SPEECH APPLICATION V+ R1 10F 10F (OPTIONAL) 10k ++ V+ VCA VCA BUF OUT IN R GAIN 5 3 4 14 ADJUST 2 1k BUFFER 2.3k IN 6 OUTPUT 0.1F VCA 13 1k AUDIO NOISE GATE 7 +IN SET 9 R2 500k LEVEL CONTROL 10k DETECTOR 17k 11 + 1F SSM2166 ROTATION SET 12 1 8 10 POWER DOWN GND AVG CAP COMP RATIO SET + 22F 25k Figure 2. Rev. F Document Feedback 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 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 19962016 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. OUTPUT (dBu) 00357-001 00357-002SSM2166 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Typical Performance Characteristics ..............................................6 Applications ....................................................................................... 1 Theory of Operation .........................................................................8 General Description ......................................................................... 1 Applications Information .............................................................8 Functional Block Diagram and Typical Speech Application ...... 1 Signal Path ......................................................................................8 Revision History ............................................................................... 2 Level Detector ................................................................................9 Specifications ..................................................................................... 3 Control Circuitry ........................................................................ 10 Absolute Maximum Ratings ............................................................ 4 Power-Down Feature ................................................................. 12 Thermal Resistance ...................................................................... 4 PCB Layout Considerations ...................................................... 12 ESD Caution .................................................................................. 4 Outline Dimensions ....................................................................... 13 Pin Configuration and Function Descriptions ............................. 5 Ordering Guide .......................................................................... 13 REVISION HISTORY 10/2016Rev. E to Rev. F 5/2008Rev. B to Rev. C Changes to Signal Path Section ...................................................... 9 Updated Format .................................................................. Universal Changes to Compression Ratio Section ...................................... 10 Changes to Features Section and General Description Section ........ 1 Changes to Downward Expansion Threshold Section .............. 11 Changes to Table 1 ............................................................................. 3 Changes to PCB Layout Considerations Section ....................... 12 Changes to Table 2 ............................................................................. 4 Deleted Evaluation Board Section and Figure 26 Renumbered Deleted TPC 3 Renumbered Sequentially ..................................... 4 Sequentially ..................................................................................... 13 Changes to Table 4, Pin 8 Description Column ............................ 5 Changes to Figure 5, Figure 6, Figure 8, and Figure 9 .................. 6 Deleted Figure 27 to Figure 29, Evaluation Board Examples Section, and Table 5 Renumbered Sequentially ....................... 14 Change to Figure 11 .......................................................................... 7 Deleted Figure 30, Evaluation Board Setup Procedure Section, Changes to Signal Path Section ....................................................... 9 Test Equipment Setup Section, and Figure 31 ............................ 15 Added Figure 19 ............................................................................. 10 Deleted Setup Summary Section, Table 6, and Table 7 ............. 16 Deleted Figure 14 and Figure 17................................................... 12 Deleted Other Versions Section ................................................... 13 10/2013Rev. D to Rev. E Changes to Figure 26 ...................................................................... 13 Change to Compression Ratio Section ........................................ 10 Changes to Figure 27 ...................................................................... 14 Changes to Ordering Guide .......................................................... 17 Changes to Test Equipment Section ............................................ 15 Added Table 6 ................................................................................. 16 7/2008Rev. C to Rev. D Added Table 7 ................................................................................. 16 Changes to Figure 4 through Figure 9 ........................................... 6 Updated Outline Dimensions ....................................................... 17 Changes to Figure 11 and Figure 12 ............................................... 7 Changes to Ordering Guide .......................................................... 17 Changes to Figure 19 ...................................................................... 10 Changes to Figure 26 ...................................................................... 13 3/2003Rev. A to Rev. B Deleted PDIP Package ....................................................... Universal Added Top Branding Revision Reflecting Die Replacement Table ................................................................................................. 17 Change to General Description ....................................................... 1 Changes to Thermal Characteristics ............................................... 2 Changes to Ordering Guide ............................................................. 2 Deleted 14-Lead PDIP, Outline Dimensions .............................. 15 Updated 14-Lead Narrow-Body SOIC, Outline Dimensions ... 15 Rev. F Page 2 of 13