Data Sheet

ADMP504

Rev. 0 | Page 7 of 12

APPLICATIONS INFORMATION

The ADMP504 output can be connected to a dedicated codec

microphone input (see Figure 8) or to a high input impedance

gain stage (see Figure 9). A 0.1 µF ceramic capacitor placed close

to the ADMP504 supply pin is used for testing and is recom-

mended 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 codec’s input impedance.

A minimum value of 2.2 μF is recommended in Figure 8

because the input impedance of the ADAU1361/ADAU1761

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

would result in a high-pass filter corner frequency at about

37 Hz.

Figure 9 shows the ADMP504 connected to an ADA4897-1

op amp configured as a noninverting preamplifier.

ADAU1761

OR

ADAU1361

ADMP504

GND

OUTPUT

LINN

LINP

MICBIAS

CM

2.2µF

MINIMUM

0.1µF

Figure 8. ADMP504 Connected to the Analog Devices ADAU1761

or ADAU1361 Codec

GAIN = (R1 + R2)/R1

ADMP504

GND

OUTPUT

1µF

MINIMUM

0.1µF

10k

Ω

R1

R2

ADA4897-1

Figure 9. ADMP504 Connected to the ADA4897-1 Op Amp

SUPPORTING DOCUMENTS

Evaluation Board User Guide

UG-325, EVAL-ADMP504-FLEX: Bottom-Ported Analog Output

MEMS Microphone Evaluation Board

Circuit Note

CN-0207, High Performance iMEMS Analog Microphone’s

Simple Interface to SigmaDSP Audio Codec

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