MAX9814_09 Datasheet, PDF (1/14 Pages) Maxim Integrated Products – Microphone Amplifier with AGC and Low-Noise Microphone Bias

19-0764; Rev 2; 6/09
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Microphone Amplifier with AGC and
Low-Noise Microphone Bias
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
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
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, 14-Pin TDFN (3mm
x 3mm) Package
o -40°C to +85°C Extended Temperature Range
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX9814ETD+T
-40°C to +85°C 14 TDFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Pin Configurations appear at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
Simplified Block Diagram
2.7V TO 5.5V
R_MICBIAS
MICBIAS
C_IN
MICIN
LOW-NOISE
REFERENCE
SHDN
V_DD
AGC
LNA
+12dB
VGA
+20dB/0dB
GND
MAX9814
GAIN
+8/+18/
+28dB
C_OUT
MICOUT
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.