INMP621

Figure 14. Stereo PDM Microphone Connection to Codec

Decouple the VDD pin of the INMP621 to GND with a 0.1 µF capacitor. Place this capacitor as close to VDD as the printed circuit board

(PCB) layout allows.

Do not use a pull-up or pull-down resistor on the PDM data signal line because it can pull the signal to an incorrect state during the period

that the signal line is tristated.

The DATA signal does not need to be buffered in normal use when the INMP621 microphone(s) is placed close to the codec on the PCB. If the DATA

signal

must be driven over a long cable (>15 cm) or other large capacitive load, a digital buffer may be required. Only use a signal buffer on the

DATA line when one microphone is in use or after the point where two microphones are connected (see Figure 15). The DATA output of

each microphone in a stereo configuration cannot be individually buffered because the two buffer outputs cannot drive a single signal line. If a

buffer is used, take care to select one with low propagation delay so that the timing of the data connected to the codec is not corrupted.

CLOCK OUTPUT

CODEC

0.1µF

1.8 V TO 3.3 V

GND

L/R SELECT

DATA

INMP621

CLK

VDD

DATA INPUT

0.1µF

1.8 V TO 3.3 V

GND

L/R SELECT

DATA

INMP621

CLK

VDD

Page 13 of 20

Document Number: DS-INMP621-00

Revision: 1.0

Rev Date: 02/06/2014