Low Voltage Microphone Preamplifier with Variable ...

1 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 VDD. Single 3 V operation VCAIN 2. SSM2167 9 OUTPUT. Low shutdown current < 2 A SHUTDOWN 3 TOP VIEW. (Not to Scale). 8 COMPRESSION RATIO. BUFOUT 4 7 GATE THRS. Adjustable noise gate threshold 02628-001. INPUT 5 6 AVG CAP. Adjustable compression ratio Automatic limiting feature prevents ADC overload Figure 1. 10-Lead MSOP (RM Suffix). Low noise and distortion: THD + N. 20 kHz bandwidth LIMITING. THRESHOLD LIMITING. APPLICATIONS (ROTATION POINT) REGION. Desktop, portable, or palmtop computers Telephone conferencing DOWNWARD. COMPRESSION. REGION. Communication headsets EXPANSION. THRESHOLD. 1 VCA GAIN. OUTPUT (dB). Two-way communications (NOISE GATE) r Surveillance systems Karaoke and DJ mixers DOWNWARD.

2 EXPANSION. REGION. GENERAL DESCRIPTION. 1. The SSM2167 is a complete and flexible solution for conditioning 1. Microphone inputs in personal electronics and computer audio systems. It is also excellent for improving vocal clarity in com- 02628-002. VDE VRP. INPUT (dB). munications and public address systems. A low noise Voltage controlled amplifier (VCA) provides a gain that is dynamically Figure 2. General Input/Output Characteristics 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.

3 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. 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 rights of third parties that may result from its use. Specifications subject to change without notice. No One Technology Way, Box 9106, Norwood, MA 02062-9106, license is granted by implication or otherwise under any patent or patent rights of analog devices . Tel: Trademarks and registered trademarks are the property of their respective owners.

4 Fax: 2001 2011 analog devices , Inc. All rights reserved. SSM2167 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 Revision History .. 2 Setting the Compression Ratio ..9. 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. 9/11 Rev. F to Rev. G Updated Outline Dimensions .. 11. Changes to Ordering Guide .. 11 Changes to Ordering Guide .. 11. 2/11 Rev. E to Rev. F 9/03 Rev. A to Rev. B. Added Storage Temperature Range Parameter to Table 4 Deleted SSM2167-2 Universal Deleted Figure 15; Renumbered Figures Sequentially.

5 7 Changes to Ordering Guide ..3. Change to Level Detector Section and Figure 17 .. 9 Edits to Figure 2 and Figure 3 ..6. Updated Outline Dimensions .. 11 Updated Outline Dimensions ..9. 6/09 Rev. D to Rev. E 3/02 Rev. 0 to Rev. A. Change to Signal Path Section .. 8 Edits to Specifications ..2. Updated Outline Dimensions .. 11 Edits to Figure 2 and Figure 3 ..6. 2/09 Rev. C to Rev. D 7/01 Revision 0: Initial Version Changes to Figure 4, Figure 5, Figure 6, and Figure 7 .. 5. Changes to Ordering Guide .. 11. 11/07 Rev. B to Rev. C. Updated Format .. Universal Changes to PSRR .. 3. Rev. G | Page 2 of 12. Data Sheet SSM2167. SPECIFICATIONS. VS = V, f = 1 kHz, RL = 100 k , RCOMP = 0 , TA = 25 C, VIN = 100 mV rms, RGATE = 2 k , unless otherwise noted. Table 1. Parameter Symbol Test Conditions/Comments 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.

6 Total Harmonic Distortion + Noise THD + N VIN = 100 mV rms %. Input Impedance ZIN 100 k . Output Impedance ZOUT 145 . Load Drive Minimum resistive load 5 k . Maximum capacitive load 2 nF. Input Voltage Range THD + N 600 mV rms Output Voltage Range 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 RCOMP 10:1. Rotation Point 63 mV rms Noise Gate Range Maximum threshold 40 dBV. POWER SUPPLY. Supply Voltage VSY V. Supply Current ISY 5 mA. DC Output Voltage V. Power Supply Rejection Ratio PSRR VSY = V to 6 V 45 dB. SHUTDOWN. Supply Current ISY Pin 3 = GND 2 8 A. Rev. G | Page 3 of 12. SSM2167 Data Sheet ABSOLUTE MAXIMUM RATINGS. THERMAL RESISTANCE. Table 2. Parameter Rating JA is specified for worst-case conditions, that is, JA is specified for a device soldered in a 4-layer circuit board for surface-mount Supply Voltage 6V.

7 Packages. Input Voltage 6V. Operating Temperature Range 40 C to +85 C Table 3. Storage Temperature Range 65 C to +150 C Package Type JA JC Unit Junction Temperature 150 C 10-Lead MSOP (RM) 180 35 C/W. Lead Temperature (Soldering, 10 sec) 300 C. 883 (Human Body) Model 500 V. ESD CAUTION. 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. Rev. G | Page 4 of 12. Data Sheet SSM2167. TYPICAL PERFORMANCE CHARACTERISTICS. 100 1. TA = 25 C. V+ = 3V. RLOAD = 100k . COMPRESSION RATIO 2:1. ROTATION POINT = 63mV rms NOISE GATE (mV rms). THD + N (%). 10 TA = 25 C.

8 V+ = 3V. VIN FREQUENCY = 1kHz RLOAD = 100k . COMPRESSION RATIO 1:1. ROTATION POINT = 63mV rms NOISE GATE SETTING = 2mV rms 1 02628-006. 02628-003. 0 500 1000 1500 2000 2500 3000 3500 1. RGATE ( ) INPUT Voltage (V rms). Figure 3. Noise Gate vs. RGATE Figure 6. THD + N vs. Input Voltage 1 0. TA = 25 C COMPRESSION RATIO 10:1. V+ = 3V. VIN = rms 10. COMPRESSION RATIO 1:1. ROTATION POINT = 63mV rms 20. NOISE GATE SETTING = 2mV rms COMPRESSION RATIO 5:1. OUTPUT (dBV). 30. THD + N (%). COMPRESSION RATIO 2:1. 40. COMPRESSION RATIO 1:1. 50. 60 TA = 25 C. V+ = 3V. 70 RLOAD = 100k . ROTATION POINT = 63mV rms NOISE GATE SETTING = 2mV rms 80. 02628-007. 02628-004. 20 100 1k 10k 30k 80 70 60 50 40 30 20 10. FREQUENCY (Hz) INPUT (dBV). Figure 4. THD + N vs. Frequency Figure 7. Output vs. Input Characteristics 35 10. V+ = 3V + 30 RGATE = 5k . 20 RCOMP = 0 . 25. 20 30. 15. PSRR (dB).

9 GAIN (dB). 40. 10. 50. 5. 0 60. 5 VIN = 2mV rms RCOMP = 175k 70. 10 ROTATION POINT = 63mV rms NOISE GATE SETTING = 2mV rms 15 80. 02628-005. 02628-008. 1k 10k 100k 1M 10M 10 100 1k 10k 100k FREQUENCY (Hz) FREQUENCY (Hz). Figure 5. GBW Curves vs. VCA Gain Figure 8. PSRR vs. Frequency Rev. G | Page 5 of 12. SSM2167. Voltage (50mV/DIV). Data Sheet Voltage (50mV/DIV). TA = 25 C TA = 25 C. CSYS = 10 F CSYS = 10 F. SYSTEM GAIN = 19dB SYSTEM GAIN = 8dB. RLOAD = 100k RLOAD = 100k . COMPRESSION RATIO 1:1 COMPRESSION RATIO 1:1. 02628-009. 02628-011. TIME (10 s/DIV) TIME (10 s/DIV). Figure 9. Small Signal Transient Response Figure 11. Small Signal Transient Response Voltage (500mV/DIV). Voltage (200mV/DIV). TA = 25 C TA = 25 C. CSYS = 10 F CSYS = 10 F. SYSTEM GAIN = SYSTEM GAIN = RLOAD = 100k RLOAD = 100k . COMPRESSION RATIO 1:1 COMPRESSION RATIO 1:1. 02628-010. 02628-012. TIME (10 s/DIV) TIME (10 s/DIV).

10 Figure 10. Large Signal Transient Response Figure 12. Large Signal Transient Response Rev. G | Page 6 of 12. Data Sheet SSM2167. Voltage (100mV/DIV). Voltage (100mV/DIV). 6dBV 6dBV. 66dBV. 66dBV. 85dBV. 85dBV. 02628-013. 02628-014. TIME (1s/DIV) TIME (500ms/DIV). Figure 13. RMS Level Detector Performance with CAVG = 22 F Figure 14. RMS Level Detector Performance with CAVG = F. Rev. G | Page 7 of 12. SSM2167 Data Sheet APPLICATIONS INFORMATION. The SSM2167 is a complete Microphone signal conditioning The breakpoint between the compression region and the limiting system on a single integrated circuit. Designed primarily for region is referred to as the limiting threshold or the rotation point. voice-band applications, this integrated circuit provides ampli- The term, rotation point, derives from the observation that the fication, limiting, Variable compression, and noise gate.