Analog Devices SSM2166S, SSM2166P Datasheet
Microphone Preamplifier with
INPUT – dBu
–70 0–60 –50 –40 –30 –20 –10
10
OUTPUT – dBu
0
–30
–40
–50
–60
–10
–20
RATIO = 10:1
RATIO = 2:1
RATIO = 1:1
a
Variable Compression and Noise Gating
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 (ⴞ1 dB)
Low Cost
APPLICATIONS
Microphone Preamplifier/Processor
Computer Sound Cards
Public Address/Paging Systems
Communication Headsets
Telephone Conferencing
Guitar Sustain Effects Generator
Computerized Voice Recognition
Surveillance Systems
Karaoke and DJ Mixers
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
SSM2166*
20 dB; this gain is in addition to the variable gain in other compression settings. The input buffer can also be configured for frontend gains of 0 dB to 20 dB. A downward expander (noise gate)
prevents amplification of 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
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 14-lead SOIC and P-DIP packages,
and guaranteed for operation over the extended industrial tempera-
ture range of –40°C to +85°C. For similar features/performance
in an 8-lead package, please refer to the SSM2165.
Figure 1. SSM2166 Compression and Gating Characteristics with 10 dB of Fixed Gain (The Gain Adjust Pin Can Be
Used to Vary This Fixed Gain Amount)
*Patents pending.
REV. A
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 by implication or
otherwise under any patent or patent rights of Analog Devices.
AUDIO
+IN
R2 = 10kV
+
1mF
R1 = 10kV
7
0.1mF
POWER
6
DOWN
SSM2166
12
BUF
BUFFER
1
GND
OUT
DETECTOR
10mF
53
VCA
LEVEL
AVG
CAP
10mF
++
IN
22mF
*
4
VCA
R
1kV
VCA1kV
CONTROL
10
8
+
25kV
14
V+
COMPRESSION
RATIO
SET
*OPTIONAL
2.3kV
2
VCA GAIN
ADJ
13
V
OUT
500kV
9
NOISE GATE
11
ROTATION
POINT SET
SET
17kV
Figure 2. Functional Block Diagram and Typical Speech Application
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 1999
V+
SSM2166–SPECIFICATIONS
WARNING!
ESD SENSITIVE DEVICE
(V+ = +5 V, f = 1 kHz, R
R1 = 0 Ω, R2 = ∞⍀, T
= 100 kΩ, R
L
= +25ⴗC, unless otherwise noted, VIN = 300 mV rms.)
A
= 600 kΩ, R
GATE
ROTATION
= 3 kΩ, R
COMP
= 0 Ω,
Parameter Symbol Conditions Min Typ Max Units
AUDIO SIGNAL PATH
Voltage Noise Density
e
n
Noise 20 kHz Bandwidth, V
15:1 Compression 17 nV/√Hz
= GND –109 dBu
IN
1
Total Harmonic Distortion THD+N 2nd and 3rd Harmonics, VIN = –20 dBu 0.25 0.5 %
22 kHz Low-Pass Filter
Input Impedance Z
Output Impedance Z
IN
OUT
180 kΩ
75 Ω
Load Drive Resistive 5 kΩ
Capacitive 2 nF
Buffer
Input Voltage Range 1% THD 1 V rms
Output Voltage Range 1% THD 1 V rms
VCA
Input Voltage Range 1% THD 1 V rms
Output Voltage Range 1% THD 1.4 V rms
Gain Bandwidth Product 1:1 Compression, VCA G = 60 dB 30 MHz
CONTROL SECTION
VCA Dynamic Gain Range 60 dB
VCA Fixed Gain Range –60 to +19 dB
Compression Ratio, Min 1:1
Compression Ratio, Max See Figure 5 for R
COMP/RROT
15:1
Control Feedthrough 15:1 Compression, Rotation Point = –10 dBu ±5mV
POWER SUPPLY
Supply Voltage Range V
Supply Current I
S
SY
4.5 5.5 V
7.5 10 mA
Quiescent Output Voltage Level 2.2 V
Power Supply Rejection Ratio PSRR 50 dB
POWER DOWN
Supply Current Pin 12 = V+
NOTES
1
0 dBu = 0.775 V rms.
2
Normal operation: Pin 12 = 0 V.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS
2
10 100 µA
ORDERING GUIDE
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+10 V
Audio Input Voltage . . . . . . . . . . . . . . . . . . . . .Supply Voltage
Operating Temperature Range . . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C
Junction Temperature (T
) . . . . . . . . . . . . . . . . . . . . . +150°C
J
Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . +300°C
Model Range Description Option
SSM2166P –40°C to +85°C Plastic DIP N-14
SSM2166S –40°C to +85°C Narrow SOIC SO-14
Temperature Package Package
ESD RATINGS
883 (Human Body) Model . . . . . . . . . . . . . . . . . . . . . . 2.0 kV
THERMAL CHARACTERISTICS
Thermal Resistance
14-Lead Plastic DIP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83°C/W
θ
JA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39°C/W
θ
JC
14-Lead SOIC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120°C/W
θ
JA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36°C/W
θ
JC
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the SSM2166 features proprietary ESD protection circuitry, permanent damage may
occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD
precautions are recommended to avoid performance degradation or loss of functionality.
– 2 –
REV. A
SSM2166
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 compression. The gain can be varied from 0 dB to 20 dB. For 20 dB leave the pin open. For
0 dB of fixed gain, a typical resistor value is approximately 1 kΩ. For 10 dB of fixed gain, the
resistor value is approximately 2 kΩ–3␣ kΩ. For resistor values < 1 kΩ, the VCA can attenu-
ate or mute. Refer to Figure 6.
3 VCA
4 VCA
IN
R
5 BUF OUT Input Buffer Amplifier Output Pin. Must not be loaded by capacitance to ground.
6 –IN Inverting Input to the Buffer. A 10 kΩ feedback resistor R1 from the buffer output Pin 5 to
7 AUDIO +IN Input Audio Signal. The input signal should be ac-coupled (0.1 µF typical) into this pin.
8 AVG CAP Detector Averaging Capacitor. A capacitor, 2.2 µF–22 µF, to ground from this pin is the
9 NOISE GATE SET Noise Gate Threshold Set Point. A resistor to V+ sets the level below which input signals are
10 COMP RATIO SET Compression Ratio Set Pin. A resistor to ground from this pin sets the compression ratio as
11 ROTATION SET Rotation Point Set Pin. This is set by a resistor to the positive supply. This resistor together
12 POWER DOWN Power-Down Pin. Connect to ground for normal operation. Connect to positive supply for
13 OUTPUT Output Signal.
14 V+ Positive Supply, +5 V Nominal.
VCA Input Pin. A typical connection is a 10 µF capacitor from the buffer output pin (Pin 5)
to this pin.
Inverting Input to the VCA. This input can be used as a nonground reference for the audio
input signal (see application notes).
this input pin, and a resistor R2, from this pin through a 1 µF to ground gives gains of 6 dB
to 20 dB for R2 = 10 kΩ to 1.1 kΩ.
averaging capacitor for the detector circuit.
downward-expanded. For a 0.7 mV threshold, the resistor value is approximately 380 kΩ.
Increasing the resistor value reduces the threshold. See Figure 4.
shown in Figure 1. Figure 5 gives resistor values for various rotation points.
with the gain adjust pin determines the onset of limiting. A typical value for this resistor is
17K for a 100 mV “rotation point.” Increasing the resistor value reduces the level at which
limiting occurs. Refer to Figure 9.
power-down mode.
REV. A
PIN CONFIGURATION
1
GND
VCA
VCA
IN
R
–IN
2
3
SSM2166
4
TOP VIEW
(Not to Scale)
5
6
7
GAIN ADJUST
BUF OUT
AUDIO +IN
–3–
14
V+
13
OUTPUT
12
POWER DOWN
11
ROTATION SET
10
COMP RATIO SET
NOISE GATE SET
9
AVG CAP
8
SSM2166
GAIN – dB
GAIN ADJUST RESISTOR – kV
20
6
0
0262 4 6 8 10 12 14 16 18 20 22 24
18
8
4
2
14
10
16
12
28 30
TA = +25°C
V+ = 5V
R
L
= 100kV
V
IN
= 100mV rms @ 1kHz
NOISE GATE SETTING
550mV rms
ROTATION POINT (PIN 11)
1V rms
COMPRESSION RATIO = 1:1
FREQUENCY – Hz
THD + N – %
5
1
0.1
20 30k100
0.05
1k 10k
TA = +25°C
V+ = 5V
V
IN
= 77.5mV rms @ 1kHz
COMPRESSION RATIO = 1:1
NOISE GATE SETTING
550mV rms
ROTATION POINT 1V rms
GAIN ADJUST (PIN 2) = 1.2kV
MEASUREMENT FILTER BW : 22Hz TO 30kHz
0
–10
–20
–30
–40
–50
OUTPUT – dBu
–60
–70
–80
–80 0–70 –60 –50 –40 –30 –20 –10
COMP RATIO = 15:1
COMP RATIO = 10:1
COMP RATIO = 5:1
COMP RATIO = 1:1
TA = +25°C
V+ = 5V
= 300mV rms @ 1kHz
V
IN
R
= 100kV
L
NOISE GATE SETTING
ROTATION POINT 300mV rms
GAIN ADJUST (PIN 2) = 1.25kV
INPUT – dBu
INPUT – dBu
COMP RATIO = 2:1
Figure 3. Output vs. Input Characteristics
100
TA = +25°C
V+ = 5V
= 100kV
R
L
10
1
NOISE GATE – mV rms
COMPRESSION RATIO = 2:1
ROTATION POINT
GAIN ADJUST (PIN 2) = 1.25kV
1V rms
550µV rms
Figure 6. VCA Gain vs. R
5
TA = +25°C
V+ = 5V
COMPRESSION RATIO = 1:1
NOISE GATE SETTING
ROTATION POINT 1V rms
GAIN ADJUST (PIN 2) = 1.25kV
1
VIN FREQUENCY = 1kHz
THD + N – %
0.1
(Pin 2 to GND)
GAIN
550mV rms
RL = 10kV
RL = 100kV
0.1
0 45050 100 350 400150 200 250 300 500 550 600 650
Figure 4. Noise Gate vs. R
COMPRESSION
RATIO
ROTATION POINT
100mV rms 0
300mV rms 0
1V rms 0
R
COMP
Figure 5. Compression Ratio vs. R
R
– kV
GATE
(Pin 9 to V+)
GATE
1:1 2:1 5:1 10:1 15:1
96
215
215
215
395
395
395
12.5
12.5
12.5
– kV, TYPICAL
96
96
(Pin 10 to GND)
COMP
–4–
0.05
0.01 10.1
INPUT VOLTAGE – V rms
Figure 7. THD+N (%) vs. Input (V rms)
Figure 8. THD+N (%) vs. Frequency (Hz)
REV. A
1.0
FREQUENCY – Hz
–10
–80
20 30k100 1k
–20
–30
–40
–50
–60
–70
R
COMP
= 0
R
GAIN
= 1.24kV
R
GATE
= 500kV
R
ROT
= 1.74kV
10k
V+ = 5±1V p-p
V+ = 5±0.5V p-p
PSRR – dB
10
0%
100
90
10ms
200mV
TA = +25 C
C
AVG
= 2.2mF
SYSTEM GAIN = 0dB
R
L
= 10kV
COMP RATIO = 1:1
0.1
ROTATION POINT – V rms
TA = +25°C
V+ = 5V
R
= 100kV
L
COMPRESSION RATIO = 1:1
NOISE GATE SETTING
GAIN ADJUST (PIN 2) = 1.25kV
550mV rms
SSM2166
0.01
Figure 9. Rotation Point vs. R
GAIN – dB
–10
–20
REV. A
045510 354015 20 25 30 50 55
R
ROT PT
RESISTOR – kV
5mV
100
90
10
TA = +25 C
0%
COMPRESSION RATIO = 15:1
NOISE BW = 20kHz
60 65 70 75 80 85 90
(Pin 11 to V+)
ROT PT
1s
Figure 10a. Wideband Output Noise
70
G = 60dB
60
50
G = 40dB
40
30
G = 20dB
20
10
ROTATION POINT = 1.13V rms
0
NOISE GATE SETTING = 336mV rms
R
= 40kV
COMP
= 400mV rms
V
IN
1k 1M10k 100k
FREQUENCY – Hz
Figure 10b. GBW Curves vs. VCA Gain
–5–
Figure 10c. PSRR vs. Frequency
20mV
100
90
TA = +25 C
C
= 2.2mF
10
0%
AVG
SYSTEM GAIN = 0dB
= 10kV
R
L
COMP RATIO = 1:1
10ms
Figure 11. Small Signal Transient Response
Figure 12. Large Signal Transient Response
Loading...