Rainbow Electronics MAX9814 User Manual

General Description

The MAX9814 is a low-cost, high-quality microphone
amplifier with automatic gain control (AGC) and low­noise microphone bias. The device features a low-noise
preamplifier, variable gain amplifier (VGA), output
amplifier, microphone-bias-voltage generator and AGC
control circuitry.

The low-noise preamplifier has a fixed 12dB gain, while
the VGA gain automatically adjusts from 20dB to 0dB,
depending on the output voltage and the AGC thresh­old. The output amplifier offers selectable gains of 8dB,
18dB, and 28dB. With no compression, the cascade of
the amplifiers results in an overall gain of 40dB, 50dB,
or 60dB. A trilevel digital input programs the output
amplifier gain. An external resistive divider controls the
AGC threshold and a single capacitor programs the
attack/release times. A trilevel digital input programs
the ratio of attack-to-release time. The hold time of the
AGC is fixed at 30ms. The low-noise microphone-bias­voltage generator can bias most electret microphones.

The MAX9814 is available in the space-saving 12-bump
UCSP™ (1.5mm x 2mm) and 14-pin TDFN packages.
This device is specified over the -40°C to +85°C
extended temperature range.

Applications

Features

o Automatic Gain Control (AGC)

o Three Gain Settings (40dB, 50dB, 60dB)

o Programmable Attack Time

o Programmable Attack and Release Ratio

o 2.7V to 5.5V Supply Voltage Range
o Low Input-Referred Noise Density of 30nV/√Hz

o Low THD: 0.04% (typ)

o Low-Power Shutdown Mode

o Internal Low-Noise Microphone Bias, 2V

o Available in the Space-Saving 12-Bump UCSP

(1.5mm x 2mm) and TDFN (3mm x 3mm)
Packages

o -40°C to +85°C Extended Temperature Range

MAX9814

Microphone Amplifier with AGC and

Low-Noise Microphone Bias

________________________________________________________________

Maxim Integrated Products

1

Ordering Information

Simplified Block Diagram

LOW-NOISE
REFERENCE

AGC

2.7V TO 5.5V

LNA

+12dB

VGA

+20dB/0dB

GAIN

+8/+18/

+28dB

MICBIAS

R

MICBIAS

MICIN

OUT

C

OUT

GND

C

IN

V

DD

SHDN

MAX9814

PART

TEMP RANGE

PIN­PACKAGE

PKG

CODE

MAX9814EBC+T

B12-3

MAX9814ETD+T

T1433-2

19-0764; Rev 0; 3/07

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

+

Denotes a lead-free package.

Pin Configurations appear at end of data sheet.

UCSP is a trademark of Maxim Integrated Products, Inc.

EVALUATION KIT

AVAILABLE

Digital Still Cameras

Digital Video Cameras

PDAs

Bluetooth Headsets

Entertainment Systems
(e.g., Karaoke)

Two-Way Communicators

High-Quality Portable
Recorders

IP Phones/Telephone
Conferencing

-40°C to +85°C 12 UCSP-12

-40°C to +85°C 14 TDFN-14

MAX9814

Microphone Amplifier with AGC and
Low-Noise Microphone Bias

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

DD

= 3.3V, SHDN = VDD, CCT= 470nF, CCG= 2µF, GAIN = VDD, TA= T

MIN

to T

MAX

, unless otherwise specified. Typical values are

at T

A

= +25°C.) (Note 1)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

VDDto GND..............................................................-0.3V to +6V

All Other Pins to GND.................................-0.3V to (V

DD

+ 0.3V)

Output Short-Circuit Duration.....................................Continuous

Continuous Current (OUT, MICBIAS) .............................±100mA

All Other Pins ....................................................................±20mA

Continuous Power Dissipation (T

A

= +70°C)

12-Bump UCSP (derate 6.5mW/°C above +70°C).......518mW

14-Pin TDFN (derate 16.7mW/°C above +70°C) ....1481.5mW

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

Junction Temperature......................................................+150°C

Lead Temperature (soldering, 10s) .................................+300°C

Bump Temperature (soldering) Reflow............................+235°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

GENERAL

Operating Voltage V

Supply Current I

Shutdown Supply Current I

Input-Referred Noise Density e

Output Noise BW = 20kHz 430 µV

Signal-to-Noise Ratio SNR

Dynamic Range DR (Note 2) 60 dB

Total Harmonic Distortion Plus
Noise

Amplifier Input BIAS V

Maximum Input Voltage V

Input Impedance Z

Maximum Gain A

Maximum Output Level V

Regulated Output Level AGC enabled, VTH = 0.7V 1.26 1.40 1.54 V

AGC Attack Time t

Attack/Release Ratio A/R

DD

DD

SHDN

n

THD+N

IN

IN_MAX

IN

OUT_RMS

ATTACK

Guaranteed by PSRR test 2.7 5.5 V

BW = 20kHz, all gain settings 30 nV/√Hz

BW = 22Hz to 22kHz

RMS

= 0.5mV

IN

), VIN = 30mV

P-P

DD

DD

DD

output signal)

RMS

(500mV

A-weighted 64

fIN = 1kHz, BW = 20Hz to 20kHz,

= 10kΩ, VTH = 1V (threshold = 2V

R

L

), V

P

= 1kHz, BW = 20Hz to 20kHz,

f

IN

= 10kΩ, VTH = 0.1V (threshold =

R

L

200mV

1% THD 100 mV

GAIN = V

GAIN = GND 49.5 50 50.6

GAIN = unconnected 59.5 60 60.5

GAIN = V

GAIN = GND 29.0 30 30.8Minimum Gain

GAIN = unconnected 38.7 40 40.5

1% THD+N, VTH = MICBIAS 0.707 V

CT = 470nF (Note 3) 1.1 ms

A/R = GND 1:500

A/R = V

A/R = unconnected 1:4000

, VCT = 0V

, VCT = 2V

RMS

P-

3.1 6 mA

0.01 1 µA

61

0.04

0.2

1.14 1.23 1.32 V

100 kΩ

39.5 40 40.5

18.7 20 20.5

1:2000

RMS

dB

%

P-P

dB

dB

RMS

P-P

ms/ms

MAX9814

Microphone Amplifier with AGC and

Low-Noise Microphone Bias

_______________________________________________________________________________________ 3

Note 1: Devices are production tested at TA= +25°C. Limits over temperature are guaranteed by design.
Note 2: Dynamic range is calculated using the EIAJ method. The input is applied at -60dBFS (0.707µV

RMS

), fIN= 1kHz.

Note 3: Attack time measured as time from AGC trigger to gain reaching 90% of its final value.
Note 4: CG is connected to an external DC voltage source, and adjusted until V

MICOUT

= 1.23V.

Note 5: CG connected to GND with 2.2µF.

ELECTRICAL CHARACTERISTICS (continued)

(V

DD

= 3.3V, SHDN = VDD, CCT= 470nF, CCG= 2µF, GAIN = VDD, TA= T

MIN

to T

MAX

, unless otherwise specified. Typical values are

at T

A

= +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MICOUT High Output Voltage V

MICOUT Low Output Voltage V

OH

OL

I

sourcing 1mA 2.45 V

OUT

I

sinking 1mA 3 mV

OUT

MICOUT Bias MICOUT unconnected 1.14 1.23 1.32 V

Output Impedance Z

Minimum Resistive Load R

Maximum Capacitive Drive C

Maximum Output Current I

Output Short-Circuit Current I

OUT

LOAD_MIN

LOAD_MAX

OUT_MAX

SC

1% THD, RL = 500Ω 12mA

AGC mode; VDD = 2.7V to 5.5V (Note 4) 35 50

Power-Supply Rejection Ratio PSRR

f = 217Hz, V

f = 1kHz, V

f = 10kHz, V

RIPPLE

RIPPLE

RIPPLE

MICROPHONE BIAS

Microphone Bias Voltage V

Output Resistance R

Output Noise Voltage V

MICBIAS_NOISEIMICBIAS

MICBIAS

MICBIAS

I

MICBIAS

I

MICBIAS

= 0.5mA 1.84 2.0 2.18 V
= 1mA 1 Ω

= 0.5mA, BW = 22Hz to 22kHz 5.5 µV

DC, VDD = 2.7V to 5.5V 70 80

Power-Supply Rejection Ratio PSRR

I

MICBIAS

f

IN

= 0.5mA, V

= 1kHz

TRILEVEL INPUTS (A/R, GAIN)

A/R or GAIN = V

Tri-Level Input Leakage Current

A/R or GAIN = GND

Input High Voltage V

Input Low Voltage V

Shutdown Enable Time t

Shutdown Disable Time t

IH

IL

ON

OFF

DIGITAL INPUT (SHDN)

SHDN Input Leakage Current -1 +1 µA

Input High Voltage V

Input Low Voltage V

IH

IL

AGC THRESHOLD INPUT (TH)

TH Input Leakage Current -1 +1 µA

= 100mV

= 100mV

= 100mV

RIPPLE

DD

50 Ω

5kΩ

200 pF

38 mA

(Note 5) 55

P-P

(Note 5) 52.5

P-P

(Note 5) 43

P-P

= 100mV

P-P

,

0.5V

DD

/ 180kΩ

0.5V

DD

/ 180kΩ

71

0.5V

DD

/ 100kΩ

0.5V

DD

/ 100kΩ

VDD x 0.7 V

VDD x 0.3 V

60 ms

40 ms

1.3 V

0.5V

DD

/ 50kΩ

0.5V

DD

/ 50kΩ

0.5 V

dB

RMS

dB

mA

MAX9814

Microphone Amplifier with AGC and
Low-Noise Microphone Bias

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VDD= 5V, CCT= 470nF, CCG= 2.2µF, VTH= V

MICBIAS

x 0.4, GAIN = VDD(40dB), AGC disabled, no load, RL= 10kΩ, C

OUT

= 1µF,

T

A

= +25°C, unless otherwise noted.)

GAIN vs. FREQUENCY

MAX9814 toc01

FREQUENCY (Hz)

GAIN (dB)

10k1k100

10

20

30

40

50

60

70

80

0

10 100k

GAIN = UNCONNECTED

GAIN = 0

GAIN = 1

POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX9814 toc02

FREQUENCY (Hz)

PSRR (dB)

10k1k100

-70

-60

-50

-40

-30

-20

-10

0

-80
10 100k

V

RIPPLE

= 200mV

P-P

MICBIAS POWER-SUPPLY REJECTION RATIO

vs. FREQUENCY

MAX9814 toc03

FREQUENCY (Hz)

PSRR (dB)

10k1k100

-100

-90

-80

-70

-60

-50

-40

-30

-110
10 100k

V

RIPPLE

= 200mV

P-P

SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX9814 toc04

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

5.55.04.0 4.53.53.0

2.6

2.7

2.8

2.9

3.0

3.1

3.2

3.3

3.4

3.5

2.5

2.5 6.0

SHUTDOWN CURRENT

vs. SUPPLY VOLTAGE

MAX9814 toc05

SUPPLY VOLTAGE (V)

SHUTDOWN CURRENT (nA)

5.55.04.54.03.53.0

0.1

0.2

0.3

0.4

0.5

0

2.5 6.0

MICROPHONE BIAS VOLTAGE

vs. MICROPHONE BIAS SOURCE CURRENT

MAX9814 toc06

I

MICBIAS

(mA)

V

MICBIAS

VOLTAGE (V)

252015105

0.5

1.0

1.5

2.0

2.5

0

030

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. FREQUENCY

MAX9814 toc07

FREQUENCY (Hz)

THD+N (%)

10k1k100

0.1

1

10

0.01
10 100k

V

OUT

= 800mV

RMS

TOTAL HARMONIC DISTORTION PLUS NOISE

vs. OUTPUT VOLTAGE

MAX9814 toc08

OUTPUT VOLTAGE (V

RMS

)

THD+N (%)

1.0

0.5

0.1

1

10

0.01

0 1.5

fIN = 300Hz, 1kHz,
and 3kHz

fIN = 10kHz

INPUT-REFERRED NOISE

vs. FREQUENCY

MAX9814 toc09

FREQUENCY (kHz)

INPUT-REFERRED NOISE (µV

RMS

/√Hz)

1010.1

100

10

0.01 100

1000

1

MICIN AC-COUPLED
TO GND

MAX9814

Microphone Amplifier with AGC and

Low-Noise Microphone Bias

_______________________________________________________________________________________

5

Typical Operating Characteristics (continued)

(VDD= 5V, CCT= 470nF, CCG= 2.2µF, VTH= V

MICBIAS

x 0.4, GAIN = VDD(40dB), AGC disabled, no load, RL= 10kΩ, C

OUT

= 1µF,

T

A

= +25°C, unless otherwise noted.)

MICBIAS NOISE vs. FREQUENCY

10,000

/√Hz)

1000

RMS

100

MICBIAS NOISE (nV

10

10 100k

FREQUENCY (Hz)

V

vs. V

1.00

VTH = 1V

0.75

)

RMS

(V

0.50

OUT

V

0.25

VTH = 0.5V

0

0150

OUT

VTH = 0.75V

VIN (mV

RMS

10k1k100

IN

AGC ENABLED
GAIN = 1

10050

)

MAX9814 toc10

500mV/div

MAX9814 toc13

V

MICIN

10mV/div

0V

V

MICOUT

0V

1.00

0.75

)

RMS

(V

0.50

OUT

V

0.25

0

040

SMALL-SIGNAL PULSE RESPONSE

CL = 10pF

200µs/div

V

vs. V

OUT

IN

VTH = 1V

VTH = 0.75V

VTH = 0.5V

VIN (mV

RMS

AGC ENABLED
GAIN = 0

302010

)

MAX9814 toc11

MAX9814 toc14

V

SHDN

5V/div

0V

V

MICBIAS

2V/div

0V

V

MICOUT

1V/div

0V

1.00

0.75

)

RMS

(V

0.50

OUT

V

0.25

0

015

TURN-ON RESPONSE

V

VTH = 1V

VTH = 0.5V

20ms/div

vs. V

OUT

VTH = 0.75V

AGC ENABLED
GAIN = UNCONNECTED

VIN (mV

RMS

MAX9814 toc12

IN

MAX9814 toc15

105

)

V

MICOUT

500mV/div

ATTACK TIME

MAX9814 toc16

V

MICOUT

500mV/div

0V

C

= 47nF

CT

200µs/div

0V

ATTACK TIME

200µs/div

C

CT

= 100nF

MAX9814 toc17

V

500mV/div

MICOUT

0V

HOLD AND RELEASE TIME

C

CT

A/R = GND

20ms/div

MAX9814 toc18

= 47nF