SSM2167_b.pdf

Low Voltage Microphone

Preamplifier with Variable

Compression and Noise Gating

SSM2167

FEATURES

Complete Microphone Conditioner in a 10-Lead Package

Single 3 V Operation

Low Shutdown Current < 2

PIN CONFIGURATION

Adjustable Noise Gate Threshold

Adjustable Compression Ratio

Automatic Limiting Feature Prevents ADC Overload

Low Noise and Distortion: 0.2% THD + N

20 kHz Bandwidth

10-Lead MSOP

(RM Suffix)

GND

VCA IN

SHUTDOWN

BUF OUT

INPUT

SSM2167

V DD

OUTPUT

COMPRESSION RATIO

GATE THRS

AVG CAP

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 communi-

cations 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 guaran-

teed for operation over the extended industrial temperature

range of –40°C to +85°C.

LIMITING

THRESHOLD

(ROTATION POINT)

LIMITING

REGION

DOWNWARD

EXPANSION

THRESHOLD

(NOISE GATE)

COMPRESSION

REGION

VCA GAIN

DOWNWARD

EXPANSION

REGION

V DE

INPUT – dB

V RP

Figure 1. General Input/Output Characteristics

REV. B

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. No 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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700 www.analog.com

SSM2167–SPECIFICATIONS (@ V S = 3.0 V, f = 1 kHz, R L = 100 k , R COMP = 0 , T A = 25 C, V IN = 100 mV rms,

R GATE = 2 k

, unless otherwise noted.)

Parameter

Symbol

Conditions

Min Typ

Max

Unit

AUDIO SIGNAL PATH

Voltage Noise Density

e n

10:1 Compression

nV/√

Noise

20 kHz Bandwidth, V IN = GND

–70

dBV

Total Harmonic Distortion + Noise THD + N

V IN = 100 mV rms

0.2

Input Impedance

Z IN

100

kΩ

Output Impedance

Z OUT

145

Ω

Load Drive

Minimum Resistive Load

kΩ

Maximum Capacitive Load

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

MHz

CONTROL SECTION

VCA Dynamic Gain Range

VCA Fixed Gain

Compression Ratio, Min

1:1

Compression Ratio, Max

See Table I for R COMP

10:1

Rotation Point

mV rms

Noise Gate Range

Maximum Threshold

–40

dBV

POWER SUPPLY

Supply Voltage

V SY

2.5

5.5

Supply Current

I SY

2.3

DC Output Voltage

1.4

Power Supply Rejection Ratio

PSRR

V SY = 2.5 V to 6 V

4.5

SHUTDOWN

Supply Current

I SY

Pin 3 = GND

Specifications subject to change without notice.

–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

Package Type

JA *

Unit

10-Lead MSOP (RM)

180

C/W

θ JA is specified for device soldered

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

ESD RATINGS

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 condi-

tions 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.

WARNING!

ESD SENSITIVE DEVICE

REV. B

–3–

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

SSM2167

– Typical Performance Characteristics

100

T A = 25

V+ = 3V

R LOAD = 100k

COMPRESSION RATIO 2:1

ROTATION POINT = 63mV rms

0.1

T A = 25

V+ = 3V

V IN FREQUENCY = 1kHz

R LOAD = 100k

COMPRESSION RATIO 1:1

ROTATION POINT = 63mV rms

NOISE GATE SETTING = 1.4mV rms

1 0

500

1,000

1,500

2,000

2,500

3,000

3,500

0.0 10m

0.1

R GATE –

INPUT VOLTAGE – V rms

TPC 1. Noise Gate vs. R GATE

TPC 4. THD + N vs. Input

T A = 25

COMPRESSION RATIO 10:1

V+ = 3V

V IN = 24.5mV rms

COMPRESSION RATIO 1:1

ROTATION POINT = 63mV rms

NOISE GATE SETTING = 1.4mV rms

COMPRESSION RATIO 5:1

COMPRESSION RATIO 2:1

0.1

COMPRESSION RATIO 1:1

T A = 25

V+ = 3V

R L = 100k

ROTATION POINT = 63mV rms

NOISE GATE SETTING = 1.4mV rms

0.01

100

10k

20k

30k

FREQUENCY – Hz

INPUT – dBV

TPC 2. THD + N vs. Frequency

TPC 5. Output vs. Input Characteristics

V+ = 3V + 0.1

R GATE = 5k

R COMP = 0V

ROTATION POINT = 63mV rms

NOISE GATE SETTING = 1.4mV rms

10k

100k

10M

100

10k

100k

FREQUENCY – Hz

TPC 3. GBW Curves vs. VCA Gain

TPC 6. PSRR vs. Frequency

–4–

REV. B

V IN = 2mV rms

R COMP = 175k

SSM2167

C SYS = 10 F

SYSTEM GAIN = 19dB

R LOAD = 100k

C SYS = 10 F

SYSTEM GAIN = 2.6dB

R LOAD = 100k

COMPRESSION RATIO 1:1

0 0

TIME – 10

s/DIV

TIME – 10

s/DIV

TPC 7. Small Signal Transient Response

TPC 10. Large Signal Transient Response

C SYS = 10 F

SYSTEM GAIN = 8.6dB

R LOAD = 100k

6dBV

COMPRESSION RATIO 1:1

66dBV

85dBV

0 0

TIME – 10

s/DIV

TIME – 1s/DIV

TPC 8. Large Signal Transient Response

TPC 11. RMS Level Detector Performance with

C AVG = 22 µ F

T A = 25 C

C SYS = 10 F

SYSTEM GAIN = 8dB

R LOAD = 100k

6dBV

COMPRESSION RATIO 1:1

66dBV

85dBV

0 0

TIME – 10

s/DIV

TIME – 500ms/DIV

TPC 9. Small Signal Transient Response

TPC 12. RMS Level Detector Performance with

C AVG = 2.2 µ F

REV. B

–5–

T A = 25

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