Low Voltage Microphone Preamplifier with Variable Compression and Noise Gating Data Sheet SSM2167 FEATURES PIN CONFIGURATION Complete microphone conditioner in a 10-lead package GND 1 10 V DD VCA 2 9 OUTPUT Single 3 V operation IN SSM2167 SHUTDOWN 3 8 COMPRESSION RATIO TOP VIEW Low shutdown current < 2 A (Not to Scale) BUF 4 7 GATE THRS OUT Adjustable noise gate threshold INPUT 5 6 AVG CAP Adjustable compression ratio Figure 1. 10-Lead MSOP (RM Suffix) Automatic limiting feature prevents ADC overload Low noise and distortion: 0.2% THD + N 20 kHz bandwidth LIMITING THRESHOLD LIMITING (ROTATION POINT) REGION APPLICATIONS Desktop, portable, or palmtop computers COMPRESSION Telephone conferencing REGION DOWNWARD EXPANSION VCA GAIN 1 Communication headsets THRESHOLD (NOISE GATE) r Two-way communications Surveillance systems Karaoke and DJ mixers DOWNWARD EXPANSION REGION GENERAL DESCRIPTION 1 The SSM2167 is a complete and flexible solution for conditioning 1 microphone inputs in personal electronics and computer audio V V systems. It is also excellent for improving vocal clarity in com- DE RP INPUT (dB) munications and public address systems. A low noise voltage Figure 2. General Input/Output Characteristics controlled amplifier (VCA) provides a gain that is dynamically adjusted by a control loop to maintain a set compression charac- teristic. 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 40C to +85C. Rev. G 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 www.analog.com 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. Fax: 781.461.3113 20012011 Analog Devices, Inc. All rights reserved. OUTPUT (dB) 02628-001 02628-002SSM2167 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Theory of Operation .....................................................................8 Applications ....................................................................................... 1 Signal Path ......................................................................................8 General Description ......................................................................... 1 Level Detector ................................................................................9 Pin Configuration ............................................................................. 1 Control Circuitry ...........................................................................9 Revision History ............................................................................... 2 Setting the Compression Ratio ....................................................9 Specifications ..................................................................................... 3 Setting the Noise Gate Threshold (Downward Expansion) . 10 Absolute Maximum Ratings ............................................................ 4 Rotation Point (Limiting) .......................................................... 10 Thermal Resistance ...................................................................... 4 Shutdown Feature ....................................................................... 10 ESD Caution .................................................................................. 4 PCB Layout Considerations ...................................................... 10 Typical Performance Characteristics ............................................. 5 Outline Dimensions ....................................................................... 11 Applications Information ................................................................ 8 Ordering Guide .......................................................................... 11 REVISION HISTORY 9/11Rev. F to Rev. G Updated Outline Dimensions ....................................................... 11 Changes to Ordering Guide .......................................................... 11 Changes to Ordering Guide .......................................................... 11 9/03Rev. A to Rev. B 2/11Rev. E to Rev. F Deleted SSM2167-2 Model................................................ Universal Added Storage Temperature Range Parameter to Table 2 ........... 4 Changes to Ordering Guide ............................................................. 3 Deleted Figure 15 Renumbered Figures Sequentially ................. 7 Edits to Figure 2 and Figure 3 .......................................................... 6 Change to Level Detector Section and Figure 17 ......................... 9 Updated Outline Dimensions .......................................................... 9 Updated Outline Dimensions ....................................................... 11 3/02Rev. 0 to Rev. A 6/09Rev. D to Rev. E Edits to Specifications ....................................................................... 2 Change to Signal Path Section ........................................................ 8 Edits to Figure 2 and Figure 3 .......................................................... 6 Updated Outline Dimensions ....................................................... 11 7/01Revision 0: Initial Version 2/09Rev. C to Rev. D Changes to Figure 4, Figure 5, Figure 6, and Figure 7 ................. 5 Changes to Ordering Guide .......................................................... 11 11/07Rev. B to Rev. C Updated Format .................................................................. Universal Changes to PSRR .............................................................................. 3 Rev. G Page 2 of 12