INMP401

APPLICATIONS INFORMATION

CONNECTING TO AUDIO CODECS

The INMP401 output can be connected to a dedicated codec microphone input (see Figure 6) or to a high input impedance gain

stage (see Figure 7.) A 0.1 µF ceramic capacitor placed close to the INMP401 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 6 because the input impedance of codecs

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 7 shows the INMP401 connected to an op

amp configured as a non-inverting preamplifier.

Figure 6. INMP401 Connected to a Codec

Figure 7. INMP401 Connected to an Op Amp

ADC

OR

CODEC

INMP401

GND

OUTPUT

INPUT

MICBIAS

2.2 µF

MINIMUM

0.1 µF

VDD

GAIN = (R1 + R2)/R1

INMP401

GND

OUTPUT

1µF

MINIMUM

0.1µF

10k

Ω

R1

R2

VDD

AMP

1.8-3.3 V

Page 8 of 14

Document Number: DS-INMP401-00

Revision: 1.0.