Microphone Amplifier with AGC and

Low-Noise Microphone Bias

HOLD AND RELEASE TIME

40ms/div

500mV/div

0V

HOLD AND RELEASE TIME

100ms/div

500mV/div

A/R = UNCONNECTED

0V

Pin Description

PIN

TDFN

NAME

FUNCTION

1CT

Timing Capacitor Connection. Connect a capacitor to CT to control the Attack and Release times

of 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.

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

6

MICOUT

Amplifier Output

7

GND

Ground

8

MICIN

Microphone 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 = Unconnected: Attack/Release Ratio is 1:4000

10

GAIN

Tri-Level Amplifier Gain Control.

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

TH

AGC Threshold Control. TH voltage sets gain control threshold. Connect TH to MICBIAS to disable

the AGC.

—

EP

Exposed Pad. Connect the TDFN EP to GND.

Typical Operating Characteristics (continued)

MAX9814

6

Maxim Integrated