Analog Devices SSM2167 b Datasheet

Low Voltage Microphone

Preamplifier with Variable

a

FEATURES
Complete Microphone Conditioner in a 10-Lead Package
Single 3 V Operation
Low Shutdown Current < 2 ␮A
Adjustable Noise Gate Threshold
Adjustable Compression Ratio
Automatic Limiting Feature Prevents ADC Overload
Low Noise and Distortion: 0.2% THD + N
20 kHz Bandwidth

APPLICATIONS
Desktop, Portable, or Palmtop Computers
Telephone Conferencing
Communication Headsets
Two-Way Communications
Surveillance Systems
Karaoke and DJ Mixers

GENERAL DESCRIPTION

The SSM2167 is a complete and flexible solution for conditioning
microphone inputs in personal electronics and 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 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 –40°C to +85°C.

Compression and Noise Gating

SSM2167

PIN CONFIGURATION

10-Lead MSOP

(RM Suffix)

1

GND

2

VCA

IN

SSM2167

INPUT

V

DE

COMPRESSION

3

4

5

(ROTATION POINT)

REGION

1

INPUT – dB

SHUTDOWN

DOWNWARD

EXPANSION

THRESHOLD

(NOISE GATE)

OUTPUT – dB

DOWNWARD

EXPANSION

REGION

BUF OUT

Figure 1. General Input/Output Characteristics

10

LIMITING

THRESHOLD

1

r

1

V

DD

9

OUTPUT

8

COMPRESSION RATIO

7

GATE THRS

6

AVG CAP

LIMITING

REGION

VCA GAIN

V

RP

REV. B

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use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
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Tel: [phone] www.analog.com
Fax: [phone] © 2003 Analog Devices, Inc. All rights reserved.

SSM2167–SPECIFICATIONS

(@ VS = 3.0 V, f = 1 kHz, RL = 100 k⍀, R
R

= 2 k⍀, unless otherwise noted.)

GATE

= 0 ⍀, TA = 25ⴗC, VIN = 100 mV rms,

COMP

Parameter Symbol Conditions Min Typ Max Unit

AUDIO SIGNAL PATH

Voltage Noise Density e

n

Noise 20 kHz Bandwidth, V
Total Harmonic Distortion + Noise THD + N V
Input Impedance Z
Output Impedance Z

IN

OUT

10:1 Compression 20 nV/√Hz

= GND –70 dBV

= 100 mV rms 0.2 %

IN

IN

100 kΩ
145 Ω

Load Drive Minimum Resistive Load 5 kΩ

Maximum Capacitive Load 2 nF
Input Voltage Range 0.4% THD 600 mV rms
Output Voltage Range 0.4% THD 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, Min 1:1
Compression Ratio, Max See Table I for R

COMP

10:1
Rotation Point 63 mV rms
Noise Gate Range Maximum Threshold –40 dBV

POWER SUPPLY

Supply Voltage V
Supply Current I

SY

SY

2.5 5.5 V

2.3 5 mA
DC Output Voltage 1.4 V
Power Supply Rejection Ratio PSRR VSY = 2.5 V to 6 V 4.5 mV

SHUTDOWN

Supply Current I

Specifications subject to change without notice.

SY

Pin 3 = GND 2 8 ␮A

–2–

REV. B

SSM2167

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 V

Operating Temperature Range . . . . . . . . . . . –40°C to +85°C

Junction Temperature Range . . . . . . . . . . . . . . . . . . . . 150°C

Lead Temperature Range (Soldering, 10 sec) . . . . . . . 300°C

ESD RATINGS

Package Type ␪JA* ␪

10-Lead MSOP (RM) 180 35 °C/W

*θJA is specified for worst-case conditions, i.e., θ

in 4-layer circuit board for surface-mount packages.

883 (Human Body) Model . . . . . . . . . . . . . . . . . . . . . . 500 V

*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational sections
of this specification is not implied. Exposure to absolute maximum rating condi­tions for extended periods may affect device reliability.

ORDERING GUIDE

Temperature Package

Model Range Package Description Option

SSM2167-1RM-Reel –40°C to +85°C 10-Lead Mini/micro SOIC (MSOP) RM-10
SSM2167-1RM-R2 –40°C to +85°C 10-Lead Mini/micro SOIC (MSOP) RM-10
SSM2167-EVAL Evaluation Board

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 SSM2167 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.

JC

is specified for device soldered

JA

Unit

WARNING!

ESD SENSITIVE DEVICE

REV. B

–3–

SSM2167

– Typical Performance Characteristics

100

10

NOISE GATE – mV rms

1

03,500500

1,000 1,500 2,5002,000 3,000

TPC 1. Noise Gate vs. R

1

TA = 25ⴗC
V+ = 3V

V

= 24.5mV rms

IN

COMPRESSION RATIO 1:1
ROTATION POINT = 63mV rms
NOISE GATE SETTING = 1.4mV rms

0.1

THD + N – %



0.01
20 30k

100

TA = 25ⴗC
V+ = 3V
R

= 100k⍀

LOAD

COMPRESSION RATIO 2:1
ROTATION POINT = 63mV rms

R

– ⍀

GATE

FREQUENCY – Hz

1k 10k

GATE

TPC 2. THD + N vs. Frequency

20k

1

0.1

THD + N – %

TA = 25ⴗC
V+ = 3V

V

FREQUENCY = 1kHz

IN

= 100k⍀

R

LOAD

COMPRESSION RATIO 1:1
ROTATION POINT = 63mV rms
NOISE GATE SETTING = 1.4mV rms

0.01
10m 10.1

INPUT VOLTAGE – V rms

TPC 4. THD + N vs. Input

0

COMPRESSION RATIO 10:1

ⴚ10

ⴚ20

ⴚ30

ⴚ40

ⴚ50

OUTPUT – dBV

ⴚ60

ⴚ70

ⴚ80

ⴚ80 ⴚ70

COMPRESSION RATIO 1:1

ⴚ60 ⴚ50 ⴚ40 ⴚ30 ⴚ20 ⴚ10

COMPRESSION RATIO 5:1

COMPRESSION RATIO 2:1

TA = 25ⴗC
V+ = 3V
R

= 100k⍀

L

ROTATION POINT = 63mV rms
NOISE GATE SETTING = 1.4mV rms

INPUT – dBV

TPC 5. Output vs. Input Characteristics

35

25

15

5

GAIN – dB

VIN = 2mV rms

ⴚ5

R

= 175k⍀

COMP

ROTATION POINT = 63mV rms
NOISE GATE SETTING = 1.4mV rms

ⴚ15

1k 10M10k

100k 1M

FREQUENCY – Hz

TPC 3. GBW Curves vs. VCA Gain

ⴚ10

V+ = 3V + 0.1
R

ⴚ20

R

ⴚ30

ⴚ40

ⴚ50

PSRR – dB

ⴚ60

ⴚ70

ⴚ80

10 100k100

= 5k⍀

GATE

= 0V

COMP

1k 10k

FREQUENCY – Hz

TPC 6. PSRR vs. Frequency

–4–

REV. B