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 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 lownoise

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.

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

(3mm x 3mm) Package

● -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