Datasheet

Microphone Amplifier with AGC and
Low-Noise Microphone Bias
HOLD AND RELEASE TIME
MAX9814 toc19
40ms/div
V
MICOUT
500mV/div
C
CT
= 47nF
A/R = V
DD
0V
HOLD AND RELEASE TIME
MAX9814 toc20
100ms/div
V
MICOUT
500mV/div
C
CT
= 47nF
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.
5V
DD
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 = V
DD
: Attack/Release Ratio is 1:2000
A/R = Unconnected: Attack/Release Ratio is 1:4000
10 GAIN
Tri-Level Amplifier Gain Control.
GAIN = V
DD
, 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 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)
(V
DD
= 5V, C
CT
= 470nF, C
CG
= 2.2µF, V
TH
= V
MICBIAS
x 0.4, GAIN = V
DD
(40dB), AGC disabled, no load, R
L
= 10kΩ, C
OUT
= 1µF,
T
A
= +25°C, unless otherwise noted.)
MAX9814
6
Maxim Integrated