INMP521
Ultra-Low Noise Microphone with Bottom Port and PDM Digital Output
GENERAL DESCRIPTION
APPLICATIONS
The INMP521* is a high performance, ultra-low noise, low
power, digital output, bottom-ported omnidirectional MEMS
microphone. The INMP521 consists of a MEMS microphone
element and an impedance converter amplifier followed by a
fourth-order sigma-delta (Σ-Δ) modulator. The digital
interface allows for the pulse density modulated (PDM)
output of two microphones to be time-multiplexed on a
single data line using a single clock. The INMP521 is function
and pin compatible with the INMP421 microphone, providing
an easy upgrade path.
The INMP521 has a very high signal-to-noise ratio (SNR) and
common sensitivity of −26 dBFS, making it an excellent choice
for far field applications. The INMP521 has an extended wideband frequency response resulting in natural sound with high
intelligibility. Low current consumption and a sleep mode
with less than 1 µA current consumption enables long battery
life for portable applications. The INMP521 complies with the
TIA-920 Tele-communications Telephone Terminal Equipment
Transmission Requirements for Wideband Digital Wireline
Telephones standard.
The INMP521 is available in a thin 4 mm × 3 mm × 1 mm
surface-mount package. It is reflow solder compatible with
no sensitivity degradation. The INMP521 is halide free.
*Protected by U.S. Patents 7,449,356; 7,825,484; 7,885,423; and 7,961,897.
Other patents are pending.
FUNCTIONAL BLOCK DIAGRAM
INMP521
VDD
GND
POWER
MANAGEMENT
PDM
MODULATOR
CLK
DATA
CHANNEL
SELECT
Smartphones and Feature Phones
Microphone Arrays
Tablet Computers
Teleconferencing Systems
Digital Still and Video Cameras
Bluetooth Headsets
Notebook PCs
Security and Surveillance
FEATURES
•
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•
•
•
•
•
•
•
•
•
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Small, Thin 4 × 3 × 1 mm Surface-Mount Package
Omnidirectional Response
Very High SNR of 65 dBA
Sensitivity of −26 dBFS
Wide Frequency Response from 100 Hz to 16 kHz
Low Current Consumption of 900 µA
Sleep Mode for Extended Battery Life, 15 cm) or other large capacitive load, a digital buffer may be
needed. Use a signal buffer on the DATA line only when one microphone is in use or after the point where two microphones are
connected (see Figure 13.)
INMP521
CODEC
CLOCK OUTPUT
CLK
DATA
DATA INPUT
INMP521
CLK
DATA
Figure 13. Buffered Connection Between Stereo INMP521 Devices and a Codec
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 a buffer with low propagation delay so that the timing of the
data connected to the codec is not corrupted.
When long wires are used to connect the codec to the INMP521, a 100 Ω source termination resistor can be used on the clock output
of the codec instead of a buffer to minimize signal over-shoot or ringing. Depending on the drive capability of the codec clock output,
a buffer may still be needed, as shown in Figure 13.
SLEEP MODE
The microphone enters sleep mode when the clock frequency falls below 1 kHz. In sleep mode, the microphone data output
is in a high impedance state. The current consumption of the INMP521 in sleep mode is less than 1 µA at VDD = 1.8 V.
The INMP521 enters sleep mode within 1 ms of the clock frequency falling below 1 kHz. The microphone wakes up from sleep mode
32,768 cycles after the clock becomes active. For a 2.4 MHz clock, the microphone begins to output data in 13.7 ms. The wake-up
time, as specified in Table 2, indicates the time from when the clock is enabled to when the INMP521 is consuming its specified
current.
START-UP TIME
The start-up time of the INMP521 from when the clock is active is the same as the wake-up time from sleep mode. The microphone
starts up 32,768 cycles after the clock is active.
Document Number: DS-INMP521-00
Revision: 1.1
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INMP521
SUPPORTING DOCUMENTS
For additional information, see the following documents.
EVALUATION BOARD USER GUIDE
UG-326, PDM Digital Output MEMS Microphone Evaluation Board
UG-335, EVAL-INMP521Z Bottom Port Digital Output MEMS Microphone Evaluation Board
APPLICATION NOTE (PRODUCT SPECIFIC)
AN-0078, High Performance Digital MEMS Microphone Simple Interface to a SigmaDSP Audio Codec
APPLICATION NOTES (GENERAL)
AN-1003, Recommendations for Mounting and Connecting the Invensense, Inc., Bottom-Ported MEMS Microphones
AN-1068, Reflow Soldering of the MEMS Microphone
AN-1112, Microphone Specifications Explained
AN-1124, Recommendations for Sealing Invensense, Inc., Bottom-Port MEMS Microphones from Dust and Liquid Ingress
AN-1140, Microphone Array Beamforming
Document Number: DS-INMP521-00
Revision: 1.1
Page 15 of 21
INMP521
PCB DESIGN AND LAND PATTERN LAYOUT
Lay out the PCB land pattern for the INMP521 at a 1:1 ratio to the solder pads on the microphone package (see
Dimensions shown in millimeters
Figure 14.) Take care to avoid applying solder paste to the sound hole in the PCB. Dimensions shown in millimeters
Figure 15 shows a suggested solder paste stencil pattern layout.
The response of the INMP521 is not affected by the PCB hole size, as long as the hole is not smaller than the sound port of the microphone (0.25 mm, or 0.010 inch, in diameter). A 0.5 mm to 1 mm (0.020 inch to 0.040 inch) diameter for the hole is recommended.
Align the hole in the microphone package with the hole in the PCB. The exact degree of the alignment does not affect the
performance of the microphone as long as the holes are not partially or completely blocked.
3.80
ø1.70
CENTER LINE
(0.30)
0.40 × 0.60 (4×)
0.35
(1.000)
0.90
(0.30)
2.80
ø1.10
(0.30)
0.70
(0.30)
(0.550)
2× R0.10
2.05
0.35
Dimensions shown in millimeters
Figure 14. Suggested PCB Land Pattern Layout
2.45
1.498 × 0.248
0.9
0.248 × 0.948 (2×)
0.398 × 0.298 (4×)
1.849
0.35
1.45
CENTER
LINE
0.7
1.000
1.525
1.849
0.248 × 1.148 (2×)
0.375
24°
1.17
24°
0.248 × 0.498 (2×)
1.498
0.205 WIDE
0.362 CUT (3×)
Dimensions shown in millimeters
Figure 15. Suggested Solder Paste Stencil Pattern Layout
Document Number: DS-INMP521-00
Revision: 1.1
Page 16 of 21
INMP521
ALTERNATIVE PCB LAND PATTERNS
The standard PCB land pattern of the INMP521 has a solid rectangle around the edge of the footprint (see Figure 14). In some board
designs, this rectangle can make routing the microphone signals more difficult. The rectangle is used to improve the RF immunity
performance of the INMP521; however, it is not necessary to have the 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 16 shows an example PCB land pattern with no enclosing rectangle around the edge of the part.
Figure 16. Example PCB Land Pattern with No Enclosing Rectangle
Figure 17 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 17. 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 land pattern similar to Figure 16 or Figure 17 is used on a PCB, make sure that the unconnected rectangle on the bottom of the
INMP521 is not placed directly over any exposed copper. The ring on the microphone is still at ground, and any PCB traces routed
beneath it must be properly masked to avoid short circuits.
PCB MATERIAL AND THICKNESS
The performance of the INMP521 is not affected by PCB thickness. The INMP521 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.
Document Number: DS-INMP521-00
Revision: 1.1
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INMP521
HANDLING INSTRUCTIONS
PICK AND PLACE EQUIPMENT
The MEMS microphone can be handled using standard pick-and-place and chip shooting equipment. Take care to avoid damage to the
MEMS microphone structure as follows:
• Use a standard pickup tool to handle the microphone. Because the microphone hole is on the bottom of the package, the
pickup tool can make contact with any part of the lid surface.
• Do not pick up the microphone with a vacuum tool that makes contact with the bottom side of the microphone.
Do not pull air out of or blow air into the microphone port.
• Do not use excessive force to place the microphone on the PCB.
REFLOW SOLDER
For best results, the soldering profile must be in accordance with the recommendations of the manufacturer of the solder paste used to
attach the MEMS microphone to the PCB. It is recommended that the solder reflow profile not exceed the limit conditions specified
in Figure 2 and Table 4.
BOARD WASH
When washing the PCB, ensure that water does not make contact with the microphone port. Do not use blow-off procedures or
ultrasonic cleaning.
Document Number: DS-INMP521-00
Revision: 1.1
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INMP521
OUTLINE DIMENSIONS
4.10
4.00
3.90
0.95 REF
3.54 REF
0.70
0.40 × 0.60
(Pins 1, 2, 4, 5)
PIN 1
2.05
1.70 DIA.
REFERENCE
CORNER
0.30 REF
0.90
2.48
REF
3
1
2
5
4
0.30 REF
3.10
3.00
2.90
R 0.10 (2 ×)
0.35
0.35
0.30 REF
0.30 REF
0.72 REF
3.80
BOTTOM VIEW
SIDE VIEW
0.24 REF
Figure 18. 5-Terminal Chip Array Small Outline No Lead Cavity [LGA_CAV]
4 mm × 3 mm × 1 mm Body
Dimensions shown in millimeters
PIN 1 INDICATION
PART NUMBER
521
YY XXXX
DATE CODE
LOT TRACEABILITY CODE
Figure 19. Package Marking Specification (Top View)
Document Number: DS-INMP521-00
Revision: 1.1
2.80
1.05 REF
TOP VIEW
1.10
1.00
0.90
1.10 DIA.
1.50
0.25 DIA.
(THRU HOLE)
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INMP521
ORDERING GUIDE
PART
INMP521ACEZ-R0
TEMP RANGE
−40°C to +85°C
PACKAGE
5-Terminal LGA_CAV*
QUANTITY
5,000
INMP521ACEZ-R7
−40°C to +85°C
5-Terminal LGA_CAV†
1,000
EV_INMP521-FX
—
Flexible Evaluation Board —
EV_INMP521
—
Evaluation Board
—
* – 13” Tape and Reel
† – 7” Tape and reel to be discontinued. Contact sales@invensense.com for availability.
REVISION HISTORY
REVISION DATE
REVISION
DESCRIPTION
02/06/2014
1.0
Initial Release
05/21/2014
1.1
Updated the Compliance Disclaimer
Document Number: DS-INMP521-00
Revision: 1.1
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INMP521
COMPLIANCE DECLARATION DISCLAIMER
InvenSense believes the environmental and other compliance information given in this document to be correct but cannot
guarantee accuracy or completeness. Conformity documents substantiating the specifications and component characteristics are on
file. InvenSense subcontracts manufacturing and the information contained herein is based on data received from vendors and
suppliers, which has not been validated by InvenSense.
This information furnished by InvenSense is believed to be accurate and reliable. However, no responsibility is assumed by
InvenSense for its use, or for any infringements of patents or other rights of third parties that may result from its use. Specifications
are subject to change without notice. InvenSense reserves the right to make changes to this product, including its circuits and
software, in order to improve its design and/or performance, without prior notice. InvenSense makes no warranties, neither
expressed nor implied, regarding the information and specifications contained in this document. InvenSense assumes no
responsibility for any claims or damages arising from information contained in this document, or from the use of products and
services detailed therein. This includes, but is not limited to, claims or damages based on the infringement of patents, copyrights,
mask work and/or other intellectual property rights.
Certain intellectual property owned by InvenSense and described in this document is patent protected. No license is granted by
implication or otherwise under any patent or patent rights of InvenSense. This publication supersedes and replaces all information
previously supplied. Trademarks that are registered trademarks are the property of their respective companies. InvenSense sensors
should not be used or sold in the development, storage, production or utilization of any conventional or mass-destructive weapons
or for any other weapons or life threatening applications, as well as in any other life critical applications such as medical equipment,
transportation, aerospace and nuclear instruments, undersea equipment, power plant equipment, disaster prevention and crime
prevention equipment.
©2014 InvenSense, Inc. All rights reserved. InvenSense, MotionTracking, MotionProcessing, MotionProcessor, MotionFusion,
MotionApps, DMP, AAR, and the InvenSense logo are trademarks of InvenSense, Inc. Other company and product names may be
trademarks of the respective companies with which they are associated.
©2014 InvenSense, Inc. All rights reserved.
Document Number: DS-INMP521-00
Revision: 1.1
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