INMP621

ALTERNATIVE PCB LAND PATTERNS

The standard PCB land pattern of the INMP621 has a solid rectangle around the edge of the footprint that can make routing the

microphone signals more difficult in some board designs. This rectangle is used to improve the radio frequency (RF) immunity

performance of the INMP621; however, it is not necessary to have this full rectangle connected for electrical functionality. If a design

can tolerate reduced RF immunity, this rectangle can either be broken or removed completely from the PCB footprint. Figure 18 shows

an example PCB land pattern with no enclosing rectangle around the edge of the part, and Figure 19 shows an example PCB land

pattern with the rectangle broken on two sides so that the inner pads can be more easily routed on the PCB.

Figure 18. Example PCB Land Pattern with No Enclosing Rectangle

Figure 19. Example PCB Land Pattern with Broken Enclosing Rectangle

Note that in both of these patterns, the solid ring around the sound port is still present; this ring is needed to ground the microphone and

for acoustic performance. The pad on the package connected to this ring is ground and still needs a solid electrical connection to the PCB

ground. If a pattern like one of these two examples is used on a PCB, take care that the unconnected rectangle on the bottom of the

INMP621 is not placed directly over any exposed copper. This ring on the microphone is still at ground, and any PCB traces routed

underneath it must be properly masked to avoid short circuits.

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PCB MATERIAL AND THICKNESS

The performance of the INMP621 is not affected by PCB thickness and can be mounted on either a rigid or flexible PCB. A flexible

PCB with the microphone can be attached directly to the device housing with an adhesive layer. This mounting method offers a reliable

seal around the sound port, while providing the shortest acoustic path for good sound quality.

Page 17 of 20

Document Number: DS-INMP621-00

Revision: 1.0

Rev Date: 02/06/2014