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Analog Devices SSM2166 - page 1
a SSM2166* Microphone Preamplifier with Variable Compression and Noise Gating 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 which may result from its use. No license is granted ...
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Analog Devices SSM2166 - page 2
Parameter Symbol Conditions Min Typ Max Units AUDIO SIGNAL PATH Voltage Noise Density e n 15:1 Compression 17 nV/ √ Hz Noise 20 kHz Bandwidth, V IN = GND –109 dBu 1 Total Harmonic Distortion THD+N 2nd and 3rd Harmonics, V IN = –20 dBu 0.25 0.5 % 22 kHz Low-Pass Filter Input Impedance Z IN 180 k Ω Output Impedance Z OUT 75 Ω Load Drive Res ...
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Analog Devices SSM2166 - page 3
SSM2166 REV. A –3– PIN DESCRIPTION Pin # Mnemonic Function 1 GND Ground 2 GAIN ADJUST VCA Gain Adjust Pin. A resistor from this pin to ground sets the fixed gain of the VCA. To check the setting of this pin the compression pin (Pin 10) should be grounded for no com- pression. The gain can be varied from 0 dB to 20 dB. For 20 dB leave the pin op ...
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Analog Devices SSM2166 - page 4
SSM2166 REV. A –4– 0 –80 –80 0 –70 –60 –50 –40 –30 –20 –10 –10 –40 –50 –60 –70 –20 –30 T A = +25 ° C V+ = 5V V IN = 300mV rms @ 1kHz R L = 100k V NOISE GATE SETTING 550µV rms ROTATION POINT 300mV rms GAIN ADJUST (PIN 2) = 1.25k V COMP RATIO = 1:1 COMP RATIO = 2:1 COMP RATIO = 5:1 COMP RATIO = 10:1 COMP RATIO = ...
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Analog Devices SSM2166 - page 5
SSM2166 REV. A –5– ROTATION POINT – V rms R ROT PT RESISTOR – k V 1.0 0.1 0.01 04 5 51 0 3 5 4 0 15 20 25 30 50 55 T A = +25°C V+ = 5V R L = 100k V COMPRESSION RATIO = 1:1 NOISE GATE SETTING 550 m V rms GAIN ADJUST (PIN 2) = 1.25k V 60 65 70 75 80 85 90 Figure 9. Rotation Point vs. R ROT PT (Pin 11 to V+) 10 0% 100 90 1s 5 m V T A = +25 C ...
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Analog Devices SSM2166 - page 6
SSM2166 REV. A –6– APPLICATIONS INFORMATION The SSM2166 is a complete microphone signal conditioning system on a single integrated circuit. Designed primarily for voiceband applications, this integrated circuit provides amplifi- cation, rms detection, limiting, variable compression, and down- ward expansion. An integral voltage-controlled ampli ...
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Analog Devices SSM2166 - page 7
SSM2166 REV. A –7– AUDIO +IN BUF OUT 53 2 V OUT 9 NOISE GATE 11 ROTATION POINT ADJUST 10 1 GND 13 VCA R 7 RMS LEVEL DETECTOR INPUT BUFFER VCA VCA IN SSM2166 R2 = 10k V 1 m F CONTROL CIRCUITRY 12 POWER DOWN POWER DOWN R GAIN COMPRESSION RATIO SET R COMP 8 C AVG 2.2 m F AVG CAP GAIN ADJUST OUTPUT 1k V 4 1k V C6 10 m F V+ V+ R GATE R ROT PT GND C7 ...
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Analog Devices SSM2166 - page 8
SSM2166 REV. A –8– 10 0% 100 90 100mV 1S 6dBV 66dBV 85dBV Figure 15b. RMS Level Detector Performance with C AVG = 22 µ F Control Circuitry The output of the rms level detector is a signal proportional to the log of the true rms value of the buffer output with an added dc offset. The control circuitry subtracts a dc voltage from this signal, sc ...
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Analog Devices SSM2166 - page 9
SSM2166 REV. A –9– The gain of the VCA can be reduced below 0 dB by making R GAIN smaller than 1 k Ω . Switching Pin 2 through 330 Ω or less to ground will mute the output. Either a switch connected to ground or a transistor may be used, as shown in Figure 19. To avoid audible “clicks” when using this MUTE feature, a capaci- tor (C5 in ...
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Analog Devices SSM2166 - page 10
SSM2166 REV. A –10– C X 1000pF C1 0.1 m F AUDIO IN (R S > 5k V ) 7 +IN SSM2166 NOTE: ADDITIONAL CIRCUIT DETAILS OMITTED FOR CLARITY. Figure 21. Circuit Configuration for Use with High Impedance Signal Sources The value of the C7 should be the same as C6, the capacitor value used between BUF OUT and VCA IN . This connection makes the source g ...
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Analog Devices SSM2166 - page 11
SSM2166 REV. A –11– Figure 23c. Evaluation Board Backside Metallization (Not to Scale) Signal sources are connected to the SSM2166 through a 1/8" phone jack where a 0.1 µ F capacitor couples the input signal to the SSM2166’s +IN pin (Pin 7). As shown in Figure 22 and in microphone applications, the phone jack shield can be op tionally c ...
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Analog Devices SSM2166 - page 12
SSM2166 REV. A –12– or an audio cable, then the onboard OP113 can be used. To use the OP113 buffer, insert Jumper J4 into board socket pins labeled “4” and “5” and insert Jumper J5 into board socket pins labeled “6” and “7.” If the output buffer is not required, re- move Jumper J5 and insert Jumper J4 into board socket pins “5 ...
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Analog Devices SSM2166 - page 13
SSM2166 REV. A –13– STEP 5. Adjusting the Rotation Point Set the input level to 15 mV, and observe the output on the os- cilloscope. Adjust R3—ROTATION PT ADJ CW until the output level just begins to drop, then reverse so that the output is 500 mV. You have now set the limiting to 500 mV. STEP 6. Adjusting the Compression Ratio Set the input ...
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Analog Devices SSM2166 - page 14
SSM2166 REV. A –14– SSM2166 Demo Board Parts List R1 10k* Feedback R2 10k Input R3 50k Pot Rotation Point, Adj. R4 1k Rotation Point, Fixed R5 0 Comp Ratio, Fixed R6 100k Pot Comp Ratio, Adj. R7 1M Pot Noise Gate, Adj. R8 1k Noise Gate, Fixed R9 1k Gain Adj., Fixed R10 20k Pot Gain Adj. R11 330 Mute R12 100k Power Down Pull-Up C1 0.1* Input DC ...
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Analog Devices SSM2166 - page 15
SSM2166 REV. A –15– OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 14-Lead Plastic DIP (N-14) 14 17 8 0.795 (20.19) 0.725 (18.42) 0.280 (7.11) 0.240 (6.10) PIN 1 0.325 (8.25) 0.300 (7.62) 0.015 (0.381) 0.008 (0.204) 0.195 (4.95) 0.115 (2.93) SEATING PLANE 0.022 (0.558) 0.014 (0.356) 0.060 (1.52) 0.015 (0.38) 0.210 (5.33) MAX 0.130 (3.3 ...
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