ADMP401

Data Sheet

Rev. E | Page 8 of 12

APPLICATIONS INFORMATION

The ADMP401 output can be connected to a dedicated codec

microphone input (see Figure 9) or to a high input impedance

gain stage (see Figure 10). A 0.1 µF ceramic capacitor placed

close to the ADMP401 supply pin is used for testing and is

recommended to adequately decouple the microphone from

noise on the power supply. A dc-blocking capacitor is required

at the output of the microphone. This capacitor creates a high-

pass filter with a corner frequency at

where R is the input impedance of the codec.

A minimum value of 2.2 µF is recommended in Figure 9

because the input impedance of the ADAU1361/ADAU1761

can be as low as 2 kΩ at its highest PGA gain setting, which

results in a high-pass filter corner frequency at about 37 Hz.

Figure 10 shows the ADMP401 connected to the ADA4897-1

op amp configured as a noninverting preamplifier.

CONNECTING THE ADMP401 TO A CODEC

LINN

LINP

MICBIAS

ADAU1761

OR

ADAU1361

2.2µF

MINIMUM

GND

ADMP401

OUTPUT

CM

0.1µF

Figure 9. ADMP401 Connected to the Analog Devices ADAU1761 or

ADAU1361 Codec

CONNECTING THE ADMP401 TO AN OP AMP

GAIN STAGE

1µF

MINIMUM

10kΩ

ADA4897-1

GND

ADMP401

OUTPUT

0.1µF

Figure 10. ADMP401 Connected to the ADA4897-1 Op Amp

SUPPORTING DOCUMENTS

Application Notes

AN-1003, Recommendations for Mounting and Connecting

Analog Devices, Inc., Bottom-Ported MEMS Microphones

AN-1068, Reflow Soldering of the MEMS Microphone

AN-1112, Microphone Specifications Explained

AN-1124, Recommendations for Sealing Analog Devices, Inc.,

Bottom-Port MEMS Microphones from Dust and Liquid

Ingress

AN-1140, Microphone Array Beamforming

Circuit Notes

CN-0207, High Performance Analog MEMS Microphone’s Simple

Interface to SigmaDSP Audio Codec

CN-0262, Low Noise Analog MEMS Microphone and Preamp

with Compression and Noise Gating

Evaluation Board User Guides

UG-126, EVAL-ADMP401Z: Bottom-Ported Analog Output MEMS

Microphone Evaluation Board

UG-278, EVAL-ADMP401Z-FLEX: Bottom-Ported Analog

Output MEMS Microphone Evaluation Board