MAX9814ETD+T Fast Delivery |IC PHOENIX CO.,LIMITED

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MAX9814ETD+T
Microphone Amplifier with AGC and Low-Noise Microphone Bias
AVAILABLE
EVALUATION KIT AVAILABLE
General Description
The MAX9814 is a low-cost, high-quality microphone
amplifier with automatic gain control (AGC) and low-
noise 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 thresh-
old. 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-bias-
voltage generator can bias most electret microphones.
The MAX9814 is available in the space-saving, 14-pin
TDFN package. This device is specified over the
-40°C to +85°C extended temperature range.
Applications
FeaturesAutomatic Gain Control (AGC)Three Gain Settings (40dB, 50dB, 60dB)Programmable Attack TimeProgrammable Attack and Release Ratio2.7V to 5.5V Supply Voltage RangeLow Input-Referred Noise Density of 30nV/√HzLow THD: 0.04% (typ)Low-Power Shutdown ModeInternal Low-Noise Microphone Bias, 2VAvailable in the Space-Saving, 14-Pin TDFN (3mm
x 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-NOISE
REFERENCEAGC
2.7V TO 5.5V
LNA
+12dB
VGA
+20dB/0dB
GAIN
+8/+18/
+28dB
MICBIAS
RMICBIAS
MICINMICOUT
COUT
GND
CIN
VDDSHDN
MAX9814
PARTTEMP RANGEPIN-PACKAGE
MAX9814ETD+T-40°C to +85°C14 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 Portable
Recorders
IP Phones/Telephone
Conferencing
MAX9814
Microphone Amplifier with AGC and
Low-Noise Microphone Bias
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VDD = 3.3V, SHDN= VDD, CCT= 470nF, CCG= 2µF, GAIN = VDD, TA= TMINto TMAX, unless otherwise specified. Typical values are
at 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 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 (VDD+ 0.3V)
Output Short-Circuit Duration.....................................Continuous
Continuous Current (MICOUT, MICBIAS).......................±100mA
All Other Pins....................................................................±20mA
Continuous Power Dissipation (TA= +70°C)
14-Pin TDFN-EP
(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
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
GENERAL
Operating VoltageVDDGuaranteed by PSRR test2.75.5V
Supply CurrentIDD3.16mA
Shutdown Supply CurrentISHDN0.011µA
Input-Referred Noise DensityenBW = 20kHz, all gain settings30nV/√Hz
Output NoiseBW = 20kHz430µVRMS
BW = 22Hz to 22kHz
(500mVRMS output signal)61Signal-to-Noise RatioSNR
A-weighted64
Dynamic RangeDR(Note 2)60dB
fIN = 1kHz, BW = 20Hz to 20kHz,
RL = 10kΩ , V T H = 1V ( thr eshol d = 2V P - P ) ,I N = 0.5m V R M S , V C T = 0V
Total Harmonic Distortion Plus
NoiseTHD+NfIN = 1kHz, BW = 20Hz to 20kHz,
RL = 10kΩ, VTH = 0.1V (threshold =
200mVP-P), VIN = 30mVRMS, VCT = 2V
Amplifier Input BIASVIN1.141.231.32V
Maximum Input VoltageVIN_MAX1% THD100mVP-P
Input ImpedanceZIN100kΩ
GAIN = VDD39.54040.5
GAIN = GND49.55050.6Maximum GainA
GAIN = unconnected59.56060.5
GAIN = VDD18.72020.5
GAIN = GND29.03030.8Minimum Gain
GAIN = unconnected38.74040.5
Maximum Output LevelVOUT_RMS1% THD+N, VTH = MICBIAS0.707VRMS
Regulated Output LevelAGC enabled, VTH = 0.7V1.261.401.54VP-P
AGC Attack TimetATTACKCCT = 470nF (Note 3)1.1ms
A/R = GND1:500
A/R = VDD1:2000Attack/Release RatioA/R
ms/ms
MAX9814
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.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
MICOUT High Output VoltageVOHIOUT sourcing 1mA2.45V
MICOUT Low Output VoltageVOLIOUT sinking 1mA3mV
MICOUT BiasMICOUT unconnected1.141.231.32V
Output ImpedanceZOUT50Ω
Minimum Resistive LoadRLOAD_MIN5kΩ
Maximum Capacitive DriveCLOAD_MAX200pF
Maximum Output CurrentIOUT_MAX1% THD, RL = 500Ω12mA
Output Short-Circuit CurrentISC38mA
AGC mode; VDD = 2.7V to 5.5V (Note 4)3550
f = 217Hz, VRIPPLE = 100mVP-P (Note 5)55
f = 1kHz, VRIPPLE = 100mVP-P (Note 5)52.5Power-Supply Rejection RatioPSRR
f = 10kHz, VRIPPLE = 100mVP-P (Note 5)43
MICROPHONE BIAS
Microphone Bias VoltageVMICBIASIMICBIAS = 0.5mA1.842.02.18V
Output ResistanceRMICBIASIMICBIAS = 1mA1Ω
Output Noise VoltageVMICBIAS_NOISEIMICBIAS = 0.5mA, BW = 22Hz to 22kHz5.5µVRMS
DC, VDD = 2.7V to 5.5V7080
Power-Supply Rejection RatioPSRRIMICBIAS = 0.5mA, VRIPPLE = 100mVP-P,
fIN = 1kHz71dB
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
Input High VoltageVIHVDD x 0.7V
Input Low VoltageVILVDD x 0.3V
Shutdown Enable TimetON60ms
Shutdown Disable TimetOFF40ms
DIGITAL INPUT (SHDN)
SHDN Input Leakage Current-1+1µA
Input High VoltageVIH1.3V
Input Low VoltageVIL0.5V
AGC THRESHOLD INPUT (TH)
TH Input Leakage Current-1+1µA
ELECTRICAL CHARACTERISTICS (continued)
(VDD = 3.3V, SHDN= VDD, CCT= 470nF, CCG= 2µF, GAIN = VDD, TA= TMINto TMAX, unless otherwise specified. Typical values are
at TA= +25°C.) (Note 1)
MAX9814
Microphone Amplifier with AGC and
Low-Noise Microphone Bias
Typical Operating Characteristics
(VDD= 5V, CCT= 470nF, CCG= 2.2µF, VTH= VMICBIASx 0.4, GAIN = VDD(40dB), AGC disabled, no load, RL= 10kΩ, COUT= 1µF,= +25°C, unless otherwise noted.)
GAIN vs. FREQUENCY
MAX9814 toc01
FREQUENCY (Hz)
GAIN (dB)
10k1k100100k
GAIN = UNCONNECTED
GAIN = 0
GAIN = 1
POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
MAX9814 toc02
FREQUENCY (Hz)
PSRR (dB)
10k1k100
-80100k
VRIPPLE = 200mVP-P
MICBIAS POWER-SUPPLY REJECTION RATIO
vs. FREQUENCY
FREQUENCY (Hz)
PSRR (dB)
10k1k100
-110100k
VRIPPLE = 200mVP-P
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX9814 toc04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
SHUTDOWN CURRENT
vs. SUPPLY VOLTAGE
MAX9814 toc05
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT (nA)
MICROPHONE BIAS VOLTAGE
vs. MICROPHONE BIAS SOURCE CURRENT
MAX9814 toc06
IMICBIAS (mA)
MICBIAS
VOLTAGE (V)2015105
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. FREQUENCY
MAX9814 toc07
THD+N (%)
10k1k100
0.01100k
VOUT = 800mVRMS
TOTAL HARMONIC DISTORTION PLUS NOISE
vs. OUTPUT VOLTAGE
MAX9814 toc08
THD+N (%)
fIN = 300Hz, 1kHz,
and 3kHz
fIN = 10kHz
INPUT-REFERRED NOISE
vs. FREQUENCY
MAX9814 toc09
INPUT-REFERRED NOISE (
RMS
Hz)10.1
MICIN AC-COUPLED
TO GND
MAX9814
Microphone Amplifier with AGC and
Low-Noise Microphone Bias
MICBIAS NOISE vs. FREQUENCY
MAX9814 toc10
FREQUENCY (Hz)
MICBIAS NOISE (nV
RMS
Hz)
10k1k100
10,000100k
SMALL-SIGNAL PULSE RESPONSE
MAX9814 toc11
200μs/div
VMICIN
10mV/div
VMICOUT
500mV/divCL = 10pF
TURN-ON RESPONSE
MAX9814 toc12
20ms/div
VSHDN
5V/div
VMICBIAS
2V/div
VMICOUT
1V/div
VOUT vs. VIN
MAX9814 toc13
VIN (mVRMS)
OUT
(V
RMS
VTH = 1V
VTH = 0.75V
VTH = 0.5VAGC ENABLED
GAIN = 1
VOUT vs. VIN
MAX9814 toc14
VIN (mVRMS)
OUT
(V
RMS2010
VTH = 1V
VTH = 0.75V
VTH = 0.5V
AGC ENABLED
GAIN = 0
VOUT vs. VIN
MAX9814 toc15
VIN (mVRMS)
OUT
(V
RMS5
VTH = 1V
VTH = 0.75V
VTH = 0.5V
AGC ENABLED
GAIN = UNCONNECTED
ATTACK TIME
MAX9814 toc16
200μs/div
VMICOUT
500mV/div
CCT = 47nF
ATTACK TIME
MAX9814 toc17
200μs/div
VMICOUT
500mV/div
CCT = 100nF
HOLD AND RELEASE TIME
MAX9814 toc18
20ms/div
VMICOUT
500mV/div
CCT = 47nF
A/R = GND
Typical Operating Characteristics (continued)
(VDD= 5V, CCT= 470nF, CCG= 2.2µF, VTH= VMICBIASx 0.4, GAIN = VDD(40dB), AGC disabled, no load, RL= 10kΩ, COUT= 1µF,= +25°C, unless otherwise noted.)
MAX9814
Microphone Amplifier with AGC and
Low-Noise Microphone Bias
HOLD AND RELEASE TIME
MAX9814 toc19
40ms/div
VMICOUT
500mV/div
CCT = 47nF
A/R = VDD
HOLD AND RELEASE TIME
MAX9814 toc20
100ms/div
VMICOUT
500mV/div
CCT = 47nF
A/R = UNCONNECTED
Pin Description
PIN
TDFN
NAMEFUNCTION
1CTTiming Capacitor Connection. Connect a capacitor to CT to control the Attack and Release times
of the AGC.SHDNActive-Low Shutdown ControlCGAmplifier DC Offset Adjust. Connect a 2.2µF capacitor to GND to ensure zero offset at the output.
4, 11N.C.No Connection. Connect to GND.
5VDDPower Supply. Bypass to GND with a 1µF capacitor.MICOUTAmplifier OutputGNDGroundMICINMicrophone Noninverting Input
9A/R
Tri-Level Attack and Release Ratio Select. Controls the ratio of attack time to release time for the
AGC circuit.
A/R = GND: Attack/Release Ratio is 1:500
A/R = VDD: Attack/Release Ratio is 1:2000
A/R = Unconnected: Attack/Release Ratio is 1:4000GAIN
Tri-Level Amplifier Gain Control.
GAIN = VDD, gain set to 40dB.
GAIN = GND, gain set to 50dB.
GAIN = Unconnected, uncompressed gain set to 60dB.BIASAmplifier Bias. Bypass to GND with a 0.47µF capacitor.MICBIASMicrophone Bias OutputTHAGC Threshold Control. TH voltage sets gain control threshold. Connect TH to MICBIAS to disable
the AGC.EPExposed Pad. Connect the TDFN EP to GND.
Typical Operating Characteristics (continued)
(VDD= 5V, CCT= 470nF, CCG= 2.2µF, VTH= VMICBIASx 0.4, GAIN = VDD(40dB), AGC disabled, no load, RL= 10kΩ, COUT= 1µF,= +25°C, unless otherwise noted.)
MAX9814
Microphone Amplifier with AGC and
Low-Noise Microphone Bias
MAX9814 AGC DISABLED
400μs/div
VMICIN
100mV/div
VMICOUT
(AC-COUPLED)
1V/div
MAX9814 fig01aMAX9814 AGC ENABLED
400μs/div
VMICIN
100mV/div
VMICOUT
(AC-COUPLED)
1V/div
MAX9814 fig01b
Detailed Description
The MAX9814 is a low-cost, high-quality microphone
amplifier with automatic gain control (AGC) and a low-
noise microphone bias. The MAX9814 consists of sever-
al distinct circuits: a low-noise preamplifier, a variable
gain 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 input
in three distinct stages. In the first stage, the input is
buffered and amplified through the low-noise preampli-
fier with a gain of 12dB. The second stage consists of
the 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 fixed
gain of 8dB, 18dB, 20dB is programmed through a sin-
gle tri-level logic input. With no compression from the
AGC, the MAX9814 is capable of providing 40dB,
50dB, or 60dB gain.
Automatic Gain Control (AGC)
A device without AGC experiences clipping at the output
when too much gain is applied to the input. AGC pre-
vents clipping at the output when too much gain is
applied to the input, eliminating output clipping. Figure 1
shows a comparison of an over-gained microphone
input 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 a
selectable time constant to correct for the excessive
output-voltage amplitude. This process is known as the
attack time. When the output signal subsequently low-
ers in amplitude, the gain is held at the reduced state
for a short period before slowly increasing to the nor-
mal value. This process is known as the hold and
release time. The speed at which the amplifiers adjust
to changing input signals is set by the external timing
capacitor CCTand the voltage applied to A/R. The
AGC threshold can be set by adjusting VTH. Gain
reduction is a function of input signal amplitude with a
maximum AGC attenuation of 20dB. Figure 2 shows the
effect of an input burst exceeding the preset limit, out-
put attack, hold and release times.
If the attack and release times are configured to
respond too fast, audible artifacts often described as
“pumping” or “breathing” can occur as the gain is
rapidly adjusted to follow the dynamics of the signal.
For best results, adjust the time constant of the AGC to
accommodate the source material. For applications in
which music CDs are the main audio source, a 160µs
attack time with an 80ms release time is recommend-
ed. Music applications typically require a shorter
release time than voice or movie content.
Figure 1. Microphone Input with and Without AGC
MAX9814

Partno	Mfg	Dc	Qty	Available	Descript
MAX9814ETD+T \|MAX9814ETDT	MAX	N/a	5000	avai	Microphone Amplifier with AGC and Low-Noise Microphone Bias