AVAILABLE

EVALUATION KIT AVAILABLE

Functional Diagrams

Pin Configurations appear at end of data sheet.Functional Diagrams continued at end of data sheet.UCSP is a trademark of Maxim Integrated Products, Inc.

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

General DescriptionThe MAX9814 is a low-cost, high-quality microphoneamplifier with automatic gain control (AGC) and low-noise microphone bias. The device features a low-noisepreamplifier, variable gain amplifier (VGA), outputamplifier, microphone-bias-voltage generator and AGCcontrol circuitry.

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

The MAX9814 is available in the space-saving, 14-pinTDFN package. This device is specified over the -40°C to +85°C extended temperature range.

Applications

Features♦ Automatic Gain Control (AGC)

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

♦ Programmable Attack Time

♦ Programmable Attack and Release Ratio

♦ 2.7V to 5.5V Supply Voltage Range

♦ Low Input-Referred Noise Density of 30nV/√Hz

♦ Low THD: 0.04% (typ)

♦ Low-Power Shutdown Mode

♦ Internal Low-Noise Microphone Bias, 2V

♦ Available in the Space-Saving, 14-Pin TDFN (3mmx 3mm) Package

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

Microphone Amplifier with AGC and Low-Noise Microphone Bias

Ordering Information

Simplified Block Diagram

LOW-NOISEREFERENCE AGC

2.7V TO 5.5V

LNA+12dB

VGA+20dB/0dB

GAIN+8/+18/+28dB

MICBIAS

RMICBIAS

MICIN MICOUTCOUT

GND

CIN

VDDSHDN

MAX9814

PART TEMP RANGE PIN-PACKAGE

MAX9814ETD+T -40°C to +85°C 14 TDFN-EP*

+Denotes a lead(Pb)-free/RoHS-compliant package.T = Tape and reel.*EP = Exposed pad.

Pin Configurations appear at end of data sheet.

Digital Still Cameras

Digital Video Cameras

PDAs

Bluetooth Headsets

Entertainment Systems(e.g., Karaoke)

Two-Way Communicators

High-Quality PortableRecorders

IP Phones/TelephoneConferencing

MAX9814

19-0764; Rev 2; 6/09

Microphone Amplifier with AGC and Low-Noise Microphone BiasABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS(VDD = 3.3V, SHDN = VDD, CCT = 470nF, CCG = 2µF, GAIN = VDD, TA = TMIN to TMAX, unless otherwise specified. Typical values areat TA = +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 functionaloperation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure toabsolute maximum rating conditions for extended periods may affect device reliability.

VDD to GND..............................................................-0.3V to +6VAll Other Pins to GND.................................-0.3V to (VDD + 0.3V)Output Short-Circuit Duration.....................................ContinuousContinuous Current (MICOUT, MICBIAS).......................±100mAAll Other Pins ....................................................................±20mA

Continuous Power Dissipation (TA = +70°C)14-Pin TDFN-EP

(derate 16.7mW/°C above +70°C)........................1481.5mWOperating Temperature Range ...........................-40°C to +85°CJunction Temperature ......................................................+150°CLead Temperature (soldering, 10s) .................................+300°CBump Temperature (soldering) Reflow............................+235°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

GENERAL

Operating Voltage VDD Guaranteed by PSRR test 2.7 5.5 V

Supply Current IDD 3.1 6 mA

Shutdown Supply Current ISHDN 0.01 1 µA

Input-Referred Noise Density en BW = 20kHz, all gain settings 30 nV/√Hz

Output Noise BW = 20kHz 430 µVRMS

BW = 22Hz to 22kHz(500mVRMS output signal)

61Signal-to-Noise Ratio SNR

A-weighted 64dB

Dynamic Range DR (Note 2) 60 dB

fIN = 1kHz, BW = 20Hz to 20kHz,RL = 10kΩ , V T H = 1V ( thr eshol d = 2V P - P ) ,V I N = 0.5m V R M S , V C T = 0V

0.04

Total Harmonic Distortion PlusNoise

THD+NfIN = 1kHz, BW = 20Hz to 20kHz,RL = 10kΩ, VTH = 0.1V (threshold =200mVP-P), VIN = 30mVRMS, VCT = 2V

0.2

%

Amplifier Input BIAS VIN 1.14 1.23 1.32 V

Maximum Input Voltage VIN_MAX 1% THD 100 mVP-P

Input Impedance ZIN 100 kΩGAIN = VDD 39.5 40 40.5

GAIN = GND 49.5 50 50.6Maximum Gain A

GAIN = unconnected 59.5 60 60.5

dB

GAIN = VDD 18.7 20 20.5

GAIN = GND 29.0 30 30.8Minimum Gain

GAIN = unconnected 38.7 40 40.5

dB

Maximum Output Level VOUT_RMS 1% THD+N, VTH = MICBIAS 0.707 VRMS

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

AGC Attack Time tATTACK CCT = 470nF (Note 3) 1.1 ms

A/R = GND 1:500

A/R = VDD 1:2000Attack/Release Ratio A/R

A/R = unconnected 1:4000

ms/ms

MAX9814

2 Maxim Integrated

Microphone Amplifier with AGC and Low-Noise Microphone Bias

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 (0.707µVRMS), 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 VMICOUT = 1.23V.Note 5: CG connected to GND with 2.2µF.

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

MICOUT High Output Voltage VOH IOUT sourcing 1mA 2.45 V

MICOUT Low Output Voltage VOL IOUT sinking 1mA 3 mV

MICOUT Bias MICOUT unconnected 1.14 1.23 1.32 V

Output Impedance ZOUT 50 ΩMinimum Resistive Load RLOAD_MIN 5 kΩMaximum Capacitive Drive CLOAD_MAX 200 pF

Maximum Output Current IOUT_MAX 1% THD, RL = 500Ω 1 2 mA

Output Short-Circuit Current ISC 3 8 mA

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

f = 217Hz, VRIPPLE = 100mVP-P (Note 5) 55

f = 1kHz, VRIPPLE = 100mVP-P (Note 5) 52.5Power-Supply Rejection Ratio PSRR

f = 10kHz, VRIPPLE = 100mVP-P (Note 5) 43

dB

MICROPHONE BIAS

Microphone Bias Voltage VMICBIAS IMICBIAS = 0.5mA 1.84 2.0 2.18 V

Output Resistance RMICBIAS IMICBIAS = 1mA 1 ΩOutput Noise Voltage VMICBIAS_NOISE IMICBIAS = 0.5mA, BW = 22Hz to 22kHz 5.5 µVRMS

DC, VDD = 2.7V to 5.5V 70 80

Power-Supply Rejection Ratio PSRR IMICBIAS = 0.5mA, VRIPPLE = 100mVP-P,fIN = 1kHz

71dB

TRILEVEL INPUTS (A/R, GAIN)

A/R or GAIN = VDD0.5VDD/ 180kΩ

0.5VDD/ 100kΩ

0.5VDD/ 50kΩ

Tri-Level Input Leakage Current

A/R or GAIN = GND0.5VDD/ 180kΩ

0.5VDD/ 100kΩ

0.5VDD/ 50kΩ

mA

Input High Voltage VIH VDD x 0.7 V

Input Low Voltage VIL VDD x 0.3 V

Shutdown Enable Time tON 60 ms

Shutdown Disable Time tOFF 40 ms

DIGITAL INPUT (SHDN)

SHDN Input Leakage Current -1 +1 µA

Input High Voltage VIH 1.3 V

Input Low Voltage VIL 0.5 V

AGC THRESHOLD INPUT (TH)

TH Input Leakage Current -1 +1 µA

ELECTRICAL CHARACTERISTICS (continued)(VDD = 3.3V, SHDN = VDD, CCT = 470nF, CCG = 2µF, GAIN = VDD, TA = TMIN to TMAX, unless otherwise specified. Typical values areat TA = +25°C.) (Note 1)

MAX9814

Maxim Integrated 3

Microphone Amplifier with AGC and Low-Noise Microphone Bias

Typical Operating Characteristics(VDD = 5V, CCT = 470nF, CCG = 2.2µF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1µF,TA = +25°C, unless otherwise noted.)

GAIN vs. FREQUENCY

MAX

9814

toc0

1

FREQUENCY (Hz)

GAIN

(dB)

10k1k100

10

20

30

40

50

60

70

80

010 100k

GAIN = UNCONNECTED

GAIN = 0GAIN = 1

POWER-SUPPLY REJECTION RATIO vs. FREQUENCY

MAX

9814

toc0

2

FREQUENCY (Hz)

PSRR

(dB)

10k1k100

-70

-60

-50

-40

-30

-20

-10

0

-8010 100k

VRIPPLE = 200mVP-P

MICBIAS POWER-SUPPLY REJECTION RATIOvs. FREQUENCY

MAX

9814

toc0

3

FREQUENCY (Hz)

PSRR

(dB)

10k1k100

-100

-90

-80

-70

-60

-50

-40

-30

-11010 100k

VRIPPLE = 200mVP-P

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAX

9814

toc0

4

SUPPLY VOLTAGE (V)

SUPP

LY C

URRE

NT (m

A)

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

2.52.5 6.0

SHUTDOWN CURRENT vs. SUPPLY VOLTAGE

MAX

9814

toc0

5

SUPPLY VOLTAGE (V)

SHUT

DOW

N CU

RREN

T (n

A)

5.55.04.54.03.53.0

0.1

0.2

0.3

0.4

0.5

02.5 6.0

MICROPHONE BIAS VOLTAGE vs. MICROPHONE BIAS SOURCE CURRENT

MAX

9814

toc0

6

IMICBIAS (mA)

V MIC

BIAS

VOL

TAGE

(V)

252015105

0.5

1.0

1.5

2.0

2.5

00 30

TOTAL HARMONIC DISTORTION PLUS NOISEvs. FREQUENCY

MAX

9814

toc0

7

FREQUENCY (Hz)

THD+

N (%

)

10k1k100

0.1

1

10

0.0110 100k

VOUT = 800mVRMS

TOTAL HARMONIC DISTORTION PLUS NOISEvs. OUTPUT VOLTAGE

MAX

9814

toc0

8

OUTPUT VOLTAGE (VRMS)

THD+

N (%

)

1.00.5

0.1

1

10

0.010 1.5

fIN = 300Hz, 1kHz, and 3kHz

fIN = 10kHz

INPUT-REFERRED NOISE vs. FREQUENCY

MAX

9814

toc0

9

FREQUENCY (kHz)

INPU

T-RE

FERR

ED N

OISE

(μV R

MS/

√Hz)

1010.1

100

10

0.01 100

1000

1

MICIN AC-COUPLED TO GND

MAX9814

4 Maxim Integrated

Microphone Amplifier with AGC and Low-Noise Microphone Bias

MICBIAS NOISE vs. FREQUENCY

MAX

9814

toc1

0

FREQUENCY (Hz)

MIC

BIAS

NOI

SE (n

V RM

S/√H

z)

10k1k100

100

1000

10,000

1010 100k

SMALL-SIGNAL PULSE RESPONSE

MAX

9814

toc1

1

200μs/div

VMICIN10mV/div

0V

VMICOUT500mV/div

0VCL = 10pF

TURN-ON RESPONSE

MAX

9814

toc1

2

20ms/div

VSHDN5V/div

0V

VMICBIAS2V/div

0V

VMICOUT1V/div

0V

VOUT vs. VIN

MAX

9814

toc1

3

VIN (mVRMS)

V OUT

(VRM

S)

10050

0.25

0.50

0.75

1.00

00 150

VTH = 1V

VTH = 0.75V

VTH = 0.5VAGC ENABLEDGAIN = 1

VOUT vs. VINM

AX98

14 to

c14

VIN (mVRMS)

V OUT

(VRM

S)

302010

0.25

0.50

0.75

1.00

00 40

VTH = 1V

VTH = 0.75V

VTH = 0.5VAGC ENABLEDGAIN = 0

VOUT vs. VIN

MAX

9814

toc1

5

VIN (mVRMS)

V OUT

(VRM

S)

105

0.25

0.50

0.75

1.00

00 15

VTH = 1V

VTH = 0.75V

VTH = 0.5VAGC ENABLEDGAIN = UNCONNECTED

ATTACK TIME

MAX

9814

toc1

6

200μs/div

VMICOUT500mV/div

CCT = 47nF

0V

ATTACK TIME

MAX

9814

toc1

7

200μs/div

VMICOUT500mV/div

CCT = 100nF

0V

HOLD AND RELEASE TIMEM

AX98

14 to

c18

20ms/div

VMICOUT500mV/div

CCT = 47nFA/R = GND

0V

Typical Operating Characteristics (continued)(VDD = 5V, CCT = 470nF, CCG = 2.2µF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1µF,TA = +25°C, unless otherwise noted.)

MAX9814

Maxim Integrated 5

Microphone Amplifier with AGC and Low-Noise Microphone Bias

HOLD AND RELEASE TIME

MAX

9814

toc1

9

40ms/div

VMICOUT500mV/div

CCT = 47nFA/R = VDD

0V

HOLD AND RELEASE TIME

MAX

9814

toc2

0

100ms/div

VMICOUT500mV/div

CCT = 47nFA/R = UNCONNECTED

0V

Pin Description

PIN

TDFNNAME FUNCTION

1 CTTiming Capacitor Connection. Connect a capacitor to CT to control the Attack and Release timesof the AGC.

2 SHDN Active-Low Shutdown Control

3 CG Amplifier DC Offset Adjust. Connect a 2.2µF capacitor to GND to ensure zero offset at the output.

4, 11 N.C. No Connection. Connect to GND.

5 VDD Power Supply. Bypass to GND with a 1µF capacitor.

6 MICOUT Amplifier Output

7 GND Ground

8 MICIN Microphone Noninverting Input

9 A/R

Tri-Level Attack and Release Ratio Select. Controls the ratio of attack time to release time for theAGC circuit.A/R = GND: Attack/Release Ratio is 1:500A/R = VDD: Attack/Release Ratio is 1:2000A/R = Unconnected: Attack/Release Ratio is 1:4000

10 GAIN

Tri-Level Amplifier Gain Control.GAIN = VDD, gain set to 40dB.GAIN = GND, gain set to 50dB.GAIN = Unconnected, uncompressed gain set to 60dB.

12 BIAS Amplifier Bias. Bypass to GND with a 0.47µF capacitor.

13 MICBIAS Microphone Bias Output

14 THAGC Threshold Control. TH voltage sets gain control threshold. Connect TH to MICBIAS to disablethe AGC.

— EP Exposed Pad. Connect the TDFN EP to GND.

Typical Operating Characteristics (continued)(VDD = 5V, CCT = 470nF, CCG = 2.2µF, VTH = VMICBIAS x 0.4, GAIN = VDD (40dB), AGC disabled, no load, RL = 10kΩ, COUT = 1µF,TA = +25°C, unless otherwise noted.)

MAX9814

6 Maxim Integrated

Microphone Amplifier with AGC and Low-Noise Microphone Bias

MAX9814 AGC DISABLED

400μs/div

VMICIN100mV/div

VMICOUT(AC-COUPLED)1V/div

MAX9814 fig01aMAX9814 AGC ENABLED

400μs/div

VMICIN100mV/div

VMICOUT(AC-COUPLED)1V/div

MAX9814 fig01b

0V

0V

0V

0V

Detailed DescriptionThe MAX9814 is a low-cost, high-quality microphoneamplifier with automatic gain control (AGC) and a low-noise microphone bias. The MAX9814 consists of sever-al distinct circuits: a low-noise preamplifier, a variablegain amplifier (VGA), an output amplifier, a microphone-bias-voltage generator, and AGC control circuitry.

An internal microphone bias voltage generator pro-vides a 2V bias that is suitable for most electret con-denser microphones. The MAX9814 amplifies the inputin three distinct stages. In the first stage, the input isbuffered and amplified through the low-noise preampli-fier with a gain of 12dB. The second stage consists ofthe VGA controlled by the AGC. The VGA/AGC combi-nation is capable of varying the gain from 20dB to 0dB.The output amplifier is the final stage in which a fixedgain of 8dB, 18dB, 20dB is programmed through a sin-gle tri-level logic input. With no compression from theAGC, the MAX9814 is capable of providing 40dB,50dB, or 60dB gain.

Automatic Gain Control (AGC)A device without AGC experiences clipping at the outputwhen too much gain is applied to the input. AGC pre-vents clipping at the output when too much gain isapplied to the input, eliminating output clipping. Figure 1shows a comparison of an over-gained microphoneinput with and without AGC.

The MAX9814’s AGC controls the gain by first detect-ing that the output voltage has exceeded a preset limit.The microphone amplifier gain is then reduced with aselectable time constant to correct for the excessiveoutput-voltage amplitude. This process is known as theattack time. When the output signal subsequently low-ers in amplitude, the gain is held at the reduced statefor a short period before slowly increasing to the nor-mal value. This process is known as the hold andrelease time. The speed at which the amplifiers adjustto changing input signals is set by the external timingcapacitor CCT and the voltage applied to A/R. TheAGC threshold can be set by adjusting VTH. Gainreduction is a function of input signal amplitude with amaximum AGC attenuation of 20dB. Figure 2 shows theeffect of an input burst exceeding the preset limit, out-put attack, hold and release times.

If the attack and release times are configured torespond too fast, audible artifacts often described as“pumping” or “breathing” can occur as the gain israpidly adjusted to follow the dynamics of the signal.For best results, adjust the time constant of the AGC toaccommodate the source material. For applications inwhich music CDs are the main audio source, a 160µsattack time with an 80ms release time is recommend-ed. Music applications typically require a shorterrelease time than voice or movie content.

Figure 1. Microphone Input with and Without AGC

MAX9814

Maxim Integrated 7

Attack TimeThe attack time is the time it takes for the AGC toreduce the gain after the input signal has exceeded thethreshold level. The gain attenuation during the attacktime is exponential, and defined as one-time constant.The time constant of the attack is given by 2400 x CCTseconds (where CCT is the external timing capacitor):

• Use a short attack time for the AGC to react quicklyto transient signals, such as snare drum beats(music) or gun shots (DVD).

• Use a longer attack time to allow the AGC to ignoreshort-duration peaks and only reduce the gain whena noticeable increase in loudness occurs. Short-duration peaks are not reduced, but louder pas-sages are. This allows the louder passages to bereduced in volume, thereby maximizing outputdynamic range.

Hold TimeHold time is the delay after the signal falls below thethreshold level before the release phase is initiated.Hold time is internally set to 30ms and nonadjustable.The hold time is cancelled by any signal exceeding theset threshold level, and the attack time is reinitiated.

Release TimeThe release time is how long it takes for the gain toreturn to its normal level after the output signal has fall-en below the threshold level and 30ms hold time hasexpired. Release time is defined as release from a20dB gain compression to 10% of the nominal gain set-ting after the input signal has fallen below the THthreshold and the 30ms hold time has expired. Releasetime is adjustable and has a minimum of 25ms. Therelease time is set by picking an attack time using CCT

and setting the attack-to-release time ratio by configur-ing A/R as shown in Table 1:

• Use a small ratio to maximize the speed of the AGC.

• Use a large ratio to maximize the sound quality andprevent repeated excursions above the thresholdfrom being independently adjusted by the AGC.

AGC Output ThresholdThe output threshold that activates AGC is adjustablethrough the use of an external resistive divider. Oncethe divider is set, AGC reduces the gain to match theoutput voltage to the voltage set at the TH input.

Microphone BiasThe MAX9814 features an internal low-noise micro-phone bias voltage capable of driving most electretcondenser microphones. The microphone bias is regu-lated at 2V to provide that the input signal to the low-noise preamplifier does not clip to ground.

Applications InformationProgramming Attack and Release Times

Attack and release times are set by selecting thecapacitance value between CT and GND, and by set-ting the logic state of A/R (Table 1). A/R is a tri-levellogic input that sets the attack-to-release time ratio.

The attack and release times can be selected by utiliz-ing the corresponding capacitances listed in Table 2.

Microphone Amplifier with AGC and Low-Noise Microphone Bias

10ms/div

VCT500mV/div

VMICOUT(AC-COUPLED)1V/div

ATTACKRELEASE

HOLD

0V

0V

A/R ATTACK/RELEASE RATIO

GND 1:500

VDD 1:2000

Unconnected 1:4000

Figure 2. Input Burst Exceeding AGC Limit

Table 1. Attack-and-Release Ratios

tRELEASE (ms)

CCTtATTACK

(ms) A/R =GND

A/R =VDD

A/R =UNCONNECTED

22nF 0.05 25 100 200

47nF 0.11 55 220 440

68nF 0.16 80 320 640

100nF 0.24 120 480 960

220nF 0.53 265 1060 2120

470nF 1.1 550 2200 4400

680nF 1.63 815 3260 6520

1µF 2.4 1200 4800 9600

Table 2. Attack-and-Release Time

MAX9814

8 Maxim Integrated

Setting the AGC ThresholdTo set the output-voltage threshold at which the micro-phone output is clamped, an external resistor-dividermust be connected from MICBIAS to ground with the out-put of the resistor-divider applied to TH. The voltage VTHdetermines the peak output-voltage threshold at whichthe output becomes clamped. The maximum signalswing at the output is then limited to two times VTH andremains at that level until the amplitude of the input signalis reduced. To disable AGC, connect TH to MICBIAS.

Microphone Bias ResistorMICBIAS is capable of sourcing 20mA. Select a value forRMICBIAS that provides the desired bias current for theelectret microphone. A value of 2.2kΩ is usually sufficientfor a microphone of typical sensitivity. Consult the micro-phone data sheet for the recommended bias resistor.

Bias CapacitorThe BIAS output of the MAX9814 is internally bufferedand provides a low-noise bias. Bypass BIAS with a470nF capacitor to ground.

Input CapacitorThe input AC-coupling capacitor (CIN) and the inputresistance (RIN) to the microphone amplifier form ahighpass filter that removes any DC bias from an inputsignal (see the Typical Application Circuit/FunctionalDiagram). CIN prevents any DC components from theinput-signal source from appearing at the amplifier out-puts. The -3dB point of the highpass filter, assumingzero source impedance due to the input signal source,is given by:

Choose CIN such that f-3dB_IN is well below the lowestfrequency of interest. Setting f-3dB_IN too high affects theamplifier’s low-frequency response. Use capacitors withlow-voltage coefficient dielectrics. Aluminum electrolytic,tantalum, or film dielectric capacitors are good choicesfor AC-coupling capacitors. Capacitors with high-voltagecoefficients, such as ceramics (non-C0G dielectrics), canresult in increased distortion at low frequencies.

Output CapacitorThe output of the MAX9814 is biased at 1.23V. To elimi-nate the DC offset, an AC-coupling capacitor (COUT)must be used. Depending on the input resistance (RL)of the following stage, COUT and RL effectively form ahighpass filter. The -3dB point of the highpass filter,assuming zero output impedance, is given by:

ShutdownThe MAX9814 features a low-power shutdown mode.When SHDN goes low, the supply current drops to0.01µA, the output enters a high-impedance state, andthe bias current to the microphone is switched off.Driving SHDN high enables the amplifier. Do not leaveSHDN unconnected.

Power-Supply Bypassing and PCB Layout

Bypass the power supply with a 0.1µF capacitor toground. Reduce stray capacitance by minimizing tracelengths and place external components as close to thedevice as possible. Surface-mount components arerecommended. In systems where analog and digitalgrounds are available, connect the MAX9814 to analogground.

f1

2 R C3dB_OUTL OUT

− =× ×π

f1

2 R C3dB_ININ IN

− =× ×π

Microphone Amplifier with AGC and Low-Noise Microphone Bias

MAX9814

Maxim Integrated 9

Microphone Amplifier with AGC and Low-Noise Microphone Bias

Typical Application Circuit/Functional Diagram

AGCMICBIAS

BIAS

RMICBIAS2.21kΩ

R1150kΩ

R2100kΩ

MICINCOUT

GND

VDD

CIN0.1μF

A/R

MICBIAS

GAIN

TH

MICOUT

VDD

VDD

SHDN

CBYPASS1μF

CBIAS0.47μF

CGCCG

2.2μF

CTCCT

470nF

REF

LNA VGA

ROUT

*THE DEVICE HAS BEEN CONFIGURED WITH AN ATTACK TIME OF 1.1ms, 40dB GAIN, AND AN ATTACK-AND-RELEASE RATIO OF 1:500.

MAX9814

MAX9814

10 Maxim Integrated

Microphone Amplifier with AGC and Low-Noise Microphone Bias

Chip InformationPROCESS: BiCMOS

Pin Configuration

MAX9814

TDFN

TOP VIEW

2 4 5

13 11 10

MIC

BIAS

N.C.

GAIN

SHDN N.C.

V DD

1

14

+

THCT

3

12

BIAS

CG

6

9A/

RM

ICOU

T

7

8

MIC

INGN

D

*EP

MAX9814

Maxim Integrated 11

Microphone Amplifier with AGC and Low-Noise Microphone Bias

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

14 TDFN-EP T1433-2 21-0137

Package InformationFor the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

MAX9814

12 Maxim Integrated

Microphone Amplifier with AGC and Low-Noise Microphone Bias

COMMON DIMENSIONS

SYMBOL MIN. MAX.

A 0.70 0.80

D 2.90 3.10

E 2.90 3.10

A1 0.00 0.05

L 0.20 0.40

PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e

PACKAGE VARIATIONS

0.25 MIN.k

A2 0.20 REF.

2.00 REF0.25±0.050.50 BSC2.30±0.1010T1033-1

2.40 REF0.20±0.05- - - - 0.40 BSC1.70±0.10 2.30±0.1014T1433-1

1.50±0.10 MO229 / WEED-3

0.40 BSC - - - - 0.20±0.05 2.40 REFT1433-2 14 2.30±0.101.70±0.10

T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF

T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

2.30±0.10 MO229 / WEED-3 2.00 REF0.25±0.050.50 BSC1.50±0.1010T1033-2

0.25±0.05 2.00 REF10 0.50 BSC MO229 / WEED-32.30±0.101.50±0.10T1033MK-1

0.40 BSC - - - - 0.20±0.05 2.40 REFT1433-3F 14 2.30±0.101.70±0.10

Package Information (continued)For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

MAX9814

Maxim Integrated 13

Microphone Amplifier with AGC and Low-Noise Microphone Bias

Revision History

REVISIONNUMBER

REVISIONDATE

DESCRIPTIONPAGES

CHANGED

0 3/07 Initial release —

1 2/09Updated Ordering Information, Absolute Maximum Ratings, Pin Description, and PinConfiguration sections to include EP for TDFN package

1, 2, 6, 11

2 6/09 Removed UCSP package 1, 2, 6, 11, 12

MAX9814

14 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

© Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.

page

date

DESCRIPTION: electret condenser microphone

1 of 4

06/2008

20050 SW 112th Ave. Tualatin, Oregon 97062 phonephone 503.612.2300 faxfax 503.612.2383

PART NUMBER: CMA-4544PF-W

SPECIFICATIONS

directivity omnidirectional

sensitivity (S) -44 ±2 dB f = 1KHz, 1Pa 0dB = 1V/Pa

sensitivity reduction (ΔS-Vs) -3 dB f = 1KHz, 1Pa Vs = 3.0 ~ 2.0 V dc

operating voltage 3 V dc (standard), 10 V dc (max.)

output impedance (Zout) 2.2 KΩ f = 1KHz, 1Pa

operating frequency (f) 20 ~ 20,000 Hz

current consumption (IDSS) 0.5 mA max. Vs = 3.0 V dc RL = 2.2KΩsignal to noise ratio (S/N) 60 dBA f = 1KHz, 1Pa A-weighted

operating temperature -20 ~ +70° C

storage temperature -20 ~ +70° C

dimensions ø9.7 x 4.5 mm

weight 0.80 g max.

material Al

terminal pin type (hand soldering only)

RoHS yes

note: We use the “Pascal (Pa)” indication of sensitivity as per the recomendation of I.E.C. (International

Electrotechnical Commission). The sensitivity of “Pa” will increase 20dB compared to the “ubar”

indication. Example: -60dB (0dB = 1V/ubar) = -40dB (1V/Pa)

APPEARANCE DRAWING

page

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DESCRIPTION: electret condenser microphone

2 of 4

06/2008

20050 SW 112th Ave. Tualatin, Oregon 97062 phonephone 503.612.2300 faxfax 503.612.2383

PART NUMBER: CMA-4544PF-W

MEASUREMENT CIRCUIT

FREQUENCY RESPONSE CURVE

page

date

DESCRIPTION: electret condenser microphone

3 of 4

06/2008

20050 SW 112th Ave. Tualatin, Oregon 97062 phonephone 503.612.2300 faxfax 503.612.2383

PART NUMBER: CMA-4544PF-W

ENVIRONMENT TEST

item test condition

high temp. test After being placed in a chamber at +70°C for

72 hours.

low temp. test After being placed in a chamber at -20°C for

72 hours.

humidity test After being placed in a chamber at +40°C and

90±5% relative humidity for 240 hours.

temp. cycle test The part shall be subjected to 10 cycles. One

cycle will consist of:

evaluation standard

The part will be measured after

being placed at +25°C for 6

hours. After any tests, the

sensitivity should be within ±3dB

compared to the initial

measurement.

MECHANICAL CHARACTERISTICS

item test condition

soldering heat resistance Lead terminals are immersed in solder bath of

270 ±5°C for 2 ±0.5 seconds.

PCB wire pull strength The pull force will be applied to double lead

wire:

Horizontal 4.9N (0.5kg) for 30 seconds

vibration The part will be measured after applying a

vibration amplitude of 1.5 mm with 10 to 55 Hz

band of vibration frequency to each of the

3 perpendicular directions for 2 hours.

drop test The part will be dropped from a height of

1 m onto a 20 mm thick wooden board 3 times

in 3 axes (X, Y, Z) for a total of 9 drops.

evaluation standard

No interference in operation.

No damage or cutting off.

After any tests, the sensitivity

should be within ±3dB compared

to the initial measurement.

TEST CONDITIONS

standard test condition a) temperature: +5 ~ +35°C b) humidity: 45 - 85% c) pressure: 860-1060 mbar

judgement test condition a) temperature: +25 ±2°C b) humidity: 60 - 70% c) pressure: 860-1060 mbar

page

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DESCRIPTION: electret condenser microphone

4 of 4

06/2008

20050 SW 112th Ave. Tualatin, Oregon 97062 phonephone 503.612.2300 faxfax 503.612.2383

PART NUMBER: CMA-4544PF-W

PACKAGING

Adafruit AGC Electret Microphone Amplifier - MAX9814Created by lady ada

Last updated on 2015-06-22 11:30:12 AM EDT

235566

899

1011111111

Guide Contents

Guide ContentsOverviewAssembly

Prepare the header strip:Add the breakout board:And Solder!

Wiring and TestWiringTest!Do more!DownloadsDatasheets3D modelsSchematics

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 2 of 12

Overview

This fancy microphone amplifier module is a step above the rest, with built in automatic gaincontrol. The AGC in the amplifier means that nearby 'loud' sounds will be quieted so they don'toverwhelm & 'clip' the amplifier, and even quiet, far-away sounds will be amplified. This amplifier isgreat for when you want to record or detect audio in a setting where levels change and you don'twant to have to tweak the amplifier gain all the time.

The chip at the heart of this amp is the MAX9814 (http://adafru.it/d9r), and has a few options youcan configure with the breakout. The default 'max gain' is 60dB, but can be set to 40dB or 50dB byjumpering the Gain pin to VCC or ground. You can also change the Attack/Release ratio, from thedefault 1:4000 to 1:2000 or 1:500. The ouput from the amp is about 2Vpp max on a 1.25V DC bias,so it can be easily used with any Analog/Digital converter that is up to 3.3V input. If you want topipe it into a Line Input, just use a 1uF blocking capacitor in series.

Each order comes with one assembled and tested board, with electret mic pre-soldered on, and asmall piece of header.

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 3 of 12

Specifications:

Supply Voltage: 2.7v-5.5v @ 3mA currentOutput: 2Vpp on 1.25V biasFrequency Response: 20Hz - 20 KHzProgrammable Attack and Release RatioAutomatic gain, selectable max from 40dB, 50dB or 60dBLow Input-Referred Noise Density of 30nV/Low THD: 0.04% (typ)

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 4 of 12

Assembly

Assembly is really easy, you can use straight or 'right-angle' style headers to attach to the PCB.We'll be using the plain straight headers included

The board comes with all surface-mount components pre-soldered. The included header strip canbe soldered on for convenient use on a breadboard or with 0.1" connectors. You can also skip thisstep and solder on wires.

Prepare the header strip:Cut the strip to length if necessary. It will be easierto solder if you insert it into a breadboard - longpins down.

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 5 of 12

Add the breakout board:Place the breakout board over the pins so that theshort pins poke through the breakout pads

And Solder!Be sure to solder all 5 pins for reliable electricalcontact.

(For tips on soldering, be sure to check out ourGuide to Excellent Soldering (http://adafru.it/aTk)).

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 6 of 12

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 7 of 12

Wiring and Test

The microphone amp is thankfully quite simple to get started. No microcontroller or programmingrequired. We suggest wiring it up directly with a battery pack and headphones to start while you geta hang of how the AGC acts and responds.

You'll need a 3 or 4 AA/AAA battery pack (http://adafru.it/727)(or some external source of 3-5VDC)- we suggest batteries since they are very electrically-quiet compared to USB or wall poweradapters.

You'll also need a headphone jack, this breadboard-friendly one (http://adafru.it/1699) works great,and a 1 to 100uF electrolytic capacitor. This is just to protect your headphones from the DC biasvoltage. Just about any capacitor will work.

Find the 'cheapest' headphones you have, or use earbuds, they wont load down the microphoneamp as much! This is not a good time to use your huge Sennheiser cans. Don't connect tospeakers or you will get really horrible feedback effects

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 8 of 12

Wiring

Connect the amplifier, battery pack and headphone jack as shown above.

For the Microphone amp:

GND connects to the battery pack ground - black wireVDD connects to the battery pack positive - red wireConnect the Gain pin to VDD for now - green wireConnect the OUT pin to a 1uF-100uF capacitor (really any value will do). If the capacitor ispolarized, connect the OUT pin to the positive side - green wire

For the headphone jack

Connect the Left and Right pins together (the microphone is mono out) to the negative sideof the capacitor - yellow wires.Connect the center ground pin to the battery ground - blue wire

Test!

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 9 of 12

Now try listening to sounds on the headphones, you should notice a strange 'effect' where you canhear people from further away than your hearing is used to! Try setting the Gain pin to the GNDpin to get 10dB more gain. You can also remove the Gain wire, to set the gain to 60dB but you mayfind the gain is way too high, and it sounds 'too noisy', so we suggest sticking to 40 or 50dB formost purposes.

You can also try adjusting the A/R (attack/response) ratio by connecting the A/R pin to VDD or GNDbut we found that the default no-wire works pretty well for most purposes.

Do more!

Now that you have the amplifier tested, you can use this microphone amp just like our non-AGCboard.

Check out http://learn.adafruit.com/adafruit-microphone-amplifier-breakout/measuring-sound-levels (http://adafru.it/d9p) and http://learn.adafruit.com/adafruit-microphone-amplifier-breakout/more-cool-projects (http://adafru.it/d9q) for other projects that can be adapted to use thisamplifier.

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 10 of 12

DownloadsDatasheetsDatasheet for the MAX9814 (http://adafru.it/d9o)Datasheet for the electret mic capsule (http://adafru.it/aW6)

3D modelsThanks to Aron Rubin!

adafruit_mic_agc.pdf

http://adafru.it/frD

adafruit_mic_agc.skp

http://adafru.it/frE

Schematics

PCB Dimensional Diagram

© Adafruit Industries https://learn.adafruit.com/adafruit-agc-electret-microphone-amplifier-max9814

Page 11 of 12

© Adafruit Industries Last Updated: 2015-06-22 11:30:12 AM EDT Page 12 of 12