INMP421
Omnidirectional Microphone with Bottom Port and PDM Digital Output
GENERAL DESCRIPTION
The INMP421 is a high performance, low power, digital
output bottom-ported omnidirectional MEMS microphone.
The INMP421 consists of a MEMS microphone element and an
impedance converter amplifier followed by a fourth-order 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 INMP421 has a flat wideband frequency response,
resulting in natural sound with high intelligibility. Low current
consumption and a sleep mode enable long battery life for
portable applications. A built-in particle filter provides high
reliability. The INMP421 complies with the TIA-920
Telecommunications Telephone Terminal Equipment
Transmission Requirements for Wideband Digital Wireline
Telephones standard.
The INMP421 is available in a thin 3 × 4 × 1 mm surface-
mount package. It is reflow solder compatible with no
sensitivity degradation. The INMP421 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.
APPLICATIONS
• Feature Phones
• Tablet Computers
• Teleconferencing Systems
• Digital Still and Video Cameras
• Bluetooth Headsets
• Notebook PCs
• Security and Surveillance
FEATURES
• Small and Thin 3 × 4 × 1 mm Surface-Mount Package
• SNR of 61 dBA
• Sensitivity of −26 dBFS
• Flat Frequency Response from 100 Hz to 15 kHz
• Low Current Consumption: <650 µA
• Sleep Mode for Extended Battery Life
• High PSR of 80 dBFS
• Fourth-order Σ-Δ Modulator
• Digital PDM Output
• Compatible with Sn/Pb and Pb-Free Solder Processes
• RoHS/WEEE Compliant
FUNCTIONAL BLOCK DIAGRAM
ORDERING INFORMATION
PART
TEMP RANGE
INMP421BCEZ-R0*
−40°C to +85°C
INMP421BCEZ-R7†
−40°C to +85°C
EV_INMP421
—
EV_INMP421-FX
—
* – 13” Tape and Reel
† – 7” Tape and reel to be discontinued. Contact sales@invensense.com for
availability.
BOTTOM TOP
INMP421
ADC
POWER
MANAGEMENT
CLK
DATA
VDD
GND
PDM
MODULATOR
CHANNEL
SELECT
L/R SELECT
InvenSense reserves the right to change the detail
specifications as may be required to permit improvements
in the design of its products.
InvenSense Inc.
1745 Technology Drive, San Jose, CA 95110 U.S.A
+1(408) 988–7339
www.invensense.com
Document Number: DS-INMP421-00
Revision: 1.0.
Release Date: 02/06/2014
INMP421
TABLE OF CONTENTS
General Description ................................................................................................................................................. 1
Applications ............................................................................................................................................................. 1
Features ................................................................................................................................................................... 1
Functional Block Diagram ........................................................................................................................................ 1
Ordering Information ............................................................................................................................................... 1
Table of Contents ..................................................................................................................................................... 2
Specifications .................................................................................................................................................................. 4
Table 1. Electrical Characteristics ............................................................................................................................ 4
Table 2. Timing Characteristics ................................................................................................................................ 5
Timing Diagram ........................................................................................................................................................ 5
Absolute Maximum Ratings ............................................................................................................................................ 6
Table 3. Absolute Maximum Ratings ....................................................................................................................... 6
ESD Caution ............................................................................................................................................................. 6
Soldering Profile....................................................................................................................................................... 7
Table 4. Recommended Soldering Profile* .............................................................................................................. 7
Pin Configurations And Function Descriptions ............................................................................................................... 8
Table 5. Pin Function Descriptions ........................................................................................................................... 8
Typical Performance Characteristics ............................................................................................................................... 9
Theory Of Operation ..................................................................................................................................................... 10
PDM Data Format .................................................................................................................................................. 10
Table 6. INMP421 Channel Setting ........................................................................................................................ 10
PDM Microphone Sensitivity ................................................................................................................................. 11
Connecting PDM Microphones .............................................................................................................................. 12
Sleep Mode ............................................................................................................................................................ 14
Power Savings When Disabling One Microphone in a Multimicrophone Application ........................................... 14
Supporting Documents ................................................................................................................................................. 15
Evaluation Board User Guide ................................................................................................................................. 15
Application Note (Product Specific) ....................................................................................................................... 15
Application Notes (General) .................................................................................................................................. 15
PCB Design And Land Pattern Layout ........................................................................................................................... 16
Alternative PCB Land Patterns ............................................................................................................................... 17
PCB Material And Thickness .................................................................................................................................. 17
Handling Instructions .................................................................................................................................................... 18
Pick And Place Equipment ..................................................................................................................................... 18
Reflow Solder ......................................................................................................................................................... 18
Board Wash............................................................................................................................................................ 18
Outline Dimensions ....................................................................................................................................................... 19
Page 2 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
Ordering Guide ............................................................................................................................................................. 20
Revision History ..................................................................................................................................................... 20
Compliance Declaration Disclaimer: ..................................................................................................................... 20
Environmental Declaration Disclaimer: ................................................................................................................ 20
Page 3 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
SPECIFICATIONS
TABLE 1. ELECTRICAL CHARACTERISTICS
(TA = −40 to 85°C, VDD = 1.8 to 3.3 V, CLK = 2.4 MHz, CLOAD = 30 pF, unless otherwise noted. All minimum and maximum specifications
are guaranteed across temperature, voltage, and clock frequency specified in Table 1, unless otherwise noted. Typical specifications
are not guaranteed.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
NOTES
PERFORMANCE
Directionality
Omni
Sensitivity
1 kHz, 94 dB SPL
−29
−26
−23
dBFS
1
Signal-to-Noise Ratio (SNR)
20 Hz to 20 kHz, A-weighted
61
dBA
Equivalent Input Noise (EIN)
20 Hz to 20 kHz, A-weighted
33
dBA SPL
Dynamic Range
Derived from EIN and
maximum acoustic input
87 dB
Frequency Response
Low frequency −3 dB point
100
Hz
2
High frequency −3 dB point
15
kHz
Total Harmonic Distortion (THD)
105 dB SPL
3
%
Power-Supply Rejection (PSR)
217 Hz, 100 mVp-p square
wave superimposed on VDD =
1.8 V
−80 dBV
Maximum Acoustic Input
Peak
120
dB SPL
POWER SUPPLY
Supply Voltage (VDD )
1.62
3.63
V
Supply Current (IS)
VDD = 1.8 V
Normal
Mode
650 µA
Sleep Mode 50 µA 3
DIGITAL INPUT/OUTPUT CHARACTERISTICS
Input Voltage High (VIH )
0.65 x
VDD
V
Input Voltage Low (VIL )
0.35 x
VDD
V
Output Voltage High (V
OH
)
ILOAD = 0.5 mA
0.7 x
VDD
VDD V
Output Voltage Low (V
OH
)
ILOAD = 0.5 mA 0
0.3 x
VDD
V
Latency
<30
µs
Noise Floor
20 Hz to 20 kHz, A-weighted
−87
dBFS
Note 1: Relative to the RMS level of sine wave with positive amplitude equal to 100% logical 1s density and negative amplitude equal to 0% logical 1s density.
Note 2: See Figure 4 and Figure 5.
Note 3: The microphone enters sleep mode when the clock frequency is less than 1 kHz.
Page 4 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
TABLE 2. TIMING CHARACTERISTICS
TA = −40 to 85°C, VDD = 1.8 to 3.3 V, CLK = 2.4 MHz, CLOAD = 30 pF, unless otherwise noted. All minimum and maximum specifications
are guaranteed. Typical specifications are not guaranteed.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
NOTES
SLEEP MODE
Wake-Up Time
Time from CLK rising (f
CLK
> 1 kHz),
power on
10 ms 1
INPUT
tCLKIN Input clock period 310 1000
ns
Clock Frequency (CLK) 1.0 2.4 3.3 MHz 1
Clock Duty Cycle 40 60
%
OUTPUT
T1OUTEN
DATA1 (right) driven after falling clock
edge
30 ns
T1OUTDIS
DATA1 (right) disabled after rising
clock edge
20 ns
T2OUTEN
DATA2 (left) driven after rising clock
edge
30 ns
T2OUTDIS
DATA2 (left) disabled after falling clock
edge
20 ns
Note 1: The microphone operates at any clock frequency between 1.0 MHz and 3.3 MHz. Some specifications may not be guaranteed at frequencies other than 2.4
MHz.
TIMING DIAGRAM
Figure 1. Pulse Density Modulated Output Timing
t
CLKIN
CLK
DATA2
DATA1
t
2OUTDIS
t
1OUTDIS
t
2OUTEN
t
1OUTEN
Page 5 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
ABSOLUTE MAXIMUM RATINGS
Stress above those listed as Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only
and functional operation of the device at these conditions is not implied. Exposure to the absolute maximum ratings conditions for
extended periods may affect device reliability.
TABLE 3. ABSOLUTE MAXIMUM RATINGS
PARAMETER
RATING
Supply Voltage (VDD)
−0.3 V to +3.63 V
Digital Pin Input Voltage
−0.3 V to VDD + 0.3 V or 3.63 V, whichever is less
Sound Pressure Level
160 dB
Mechanical Shock
10,000 g
Vibration
Per MIL-STD-883 Method 2007, Test Condition B
Temperature Range
Biased
−40°C to +85°C
Storage
−55°C to +150°C
ESD CAUTION
ESD (electrostatic discharge) sensitive device.
Charged devices and circuit boards can
discharge without detection. Although this
product features patented or proprietary
protection circuitry, damage may occur on
devices subjected to high energy ESD.
Therefore proper ESD precautions should be
taken to avoid performance degradation or
loss of functionality.
Page 6 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
SOLDERING PROFILE
Figure 2. Recommended Soldering Profile Limits
TABLE 4. RECOMMENDED SOLDERING PROFILE*
PROFILE FEATURE
Sn63/Pb37
Pb-Free
Average Ramp Rate (T
L
to T
P
)
1.25°C/sec max
1.25°C/sec max
Preheat
Minimum Temperature
(TSMIN )
100°C 100°C
Minimum Temperature
(TSMIN )
150°C 200°C
Time (TSMIN to TSMAX ), tS
60 sec to 75 sec
60 sec to 75 sec
Ramp-Up Rate (T
SMAX
to T
L
) 1.25°C/sec 1.25°C/sec
Time Maintained Above Liquidous (t
L
) 45 sec to 75 sec ~50 sec
Liquidous Temperature (T
L
) 183°C 217°C
Peak Temperature (T
P
)
215°C +3°C/−3°C 260°C +0°C/−5°C
Time Within +5°C of Actual Peak
Temperature (tP)
20 sec to 30 sec 20 sec to 30 sec
Ramp-Down Rate 3°C/sec max
3°C/sec max
Time +25°C (t
25°C
) to Peak
Temperature
5 min max 5 min max
*The reflow profile in Table 3 is recommended for board manufacturing with InvenSense MEMS microphones. All
microphones are also compatible with the J-STD-020 profile.
tP
tL
t25°C
TO PEAK TEMPERATURE
tS
PREHEAT
CRITICAL ZONE
T
L
TO T
P
TEMPERATURE
TIME
RAMP-DOWN
RAMP-UP
T
SMIN
T
SMAX
T
P
T
L
Page 7 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
Figure 3. Pin Configuration
TABLE 5. PIN FUNCTION DESCRIPTIONS
PIN NAME FUNCTION
1 CLK Clock Input to Microphone
2 L/R SELECT
Left Channel or Right Channel Select:
DATA 1 (right): L/R SELECT tied to GND
DATA 2 (left): L/R SELECT tied to VDD
3 GND Ground
4 VDD
Power Supply. For best performance and to avoid potential parasitic artifacts, place a 0.1 µF
(100 nF) ceramic type X7R capacitor between Pin 4 (VDD) and ground. Place the capacitor as
close to Pin 4 as possible.
5 DATA Digital Output Signal (DATA1 or DATA2)
3
CLK
L/R SELECT
GND
DATA
VDD
4
5
2
1
Page 8 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 4. Frequency Response Mask
Figure 5. Typical Frequency Response (Measured)
Figure 6. Power-Supply Rejection (PSR) vs. Frequency
–10
–8
–6
–4
–2
0
2
4
6
8
10
100 10k
1k
FRE QUENCY ( Hz )
(dB)
10
0
–10
–20
100 1k 10k
FRE QUENCY ( Hz )
(dB)
–100
–90
–80
–70
–60
–50
–40
200 500 1k 2k 5k 10k 20k
FRE QUENCY ( Hz )
PSR (dBFS)
Page 9 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
THEORY OF OPERATION
PDM DATA FORMAT
The output from the DATA pin of the INMP421 is in PDM format. This data is the 1-bit output of a fourth-order Σ-Δ modulator. The
data is encoded so that the left channel is clocked on the falling edge of CLK and the right channel is clocked on the rising edge of
CLK.
After driving the DATA signal high or low in the appropriate half frame of the CLK signal, the DATA driver of the microphone is
tristated. In this way, two microphones—one set to the left channel and the other to the right channel—can drive a single DATA line.
Figure 1 shows a timing diagram of the PDM data format; the DATA1 and DATA2 lines shown in Figure 1 are two halves of the single
physical DATA signal. Figure 7 shows a diagram of the two stereo channels sharing a common DATA line.
Figure 7. Stereo PDM Format
If only one microphone is connected to the DATA signal, the output is clocked on a single edge only (See Figure 8.)
Figure 8. Mono PDM Format
For example, a left channel microphone is never clocked on the rising edge of CLK. In a single microphone application, each bit of the
DATA signal is typically held for the full CLK period until the next transition of the CLK signal because the leakage of the DATA line is
not sufficient to discharge the line while the driver is tristated.
The channel assignments are determined by the logic level on the L/R SELECT pin (see Table 6.)
TABLE 6. INMP421 CHANNEL SETTING
DATA2 ( L) DATA2 ( L)DATA1 ( R) DATA1 ( R)
CLK
DATA
DATA1 (R) DATA1(R) DATA1 (R)
CLK
DATA
L/R SELECT Pin Setting
Channel
Low (tie to GND)
Right (DATA1)
High (tie to VDD)
Left (DATA2)
Page 10 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
For PDM data, the density of the pulses indicates the signal amplitude. A high density of high pulses indicates a signal near positive
full scale, and a high density of low pulses indicates a signal near negative full scale. A perfect zero (dc) audio signal
is indicated by an alternating pattern of high and low pulses.
The output PDM data signal has a small dc offset of approximately 5% of full scale. A high-pass filter in the codec that is connected
to the digital microphone typically removes this dc signal and does not affect the performance of the microphone.
PDM MICROPHONE SENSITIVITY
The sensitivity of a PDM output microphone is specified in units of dBFS (decibels relative to a full-scale digital output). A 0 dBFS sine
wave is defined as a signal whose peak just touches the full-scale code of the digital word (see Figure 9). This measurement
convention means that signals with a different crest factor may have an RMS level higher than 0dBFS. For example, a full-scale
square wave has an RMS level of 3dBFS.
Figure 9. 1 kHz, 0 dBFS Sine Wave
The definition of a 0 dBFS signal must be understood when measuring the sensitivity of the INMP421. An acoustic input signal of a
1 kHz sine wave at 94 dB SPL applied to the INMP421 results in an output signal with a −26 dBFS level. This means that the output
digital word peaks at −26 dB below the digital full-scale level. A common misunderstanding is that the output has an RMS level of
−29 dBFS; however, this is not the case because of the definition of a 0 dBFS sine wave.
There is no commonly accepted unit of measurement to express the instantaneous level of a digital signal output from the
microphone, as opposed to the RMS level of the signal. Some measurement systems express the instantaneous level of an individual
sample in units of D, where 1.0 D is digital full scale (see Figure 9). In this case, a −26 dBFS sine wave has peaks at 0.05 D.
For more information about digital microphone sensitivity, see the AN-1112 Application Note, Microphone Specifications Explained.
1.0
–1.0
–0.8
–0.6
–0.4
–0.2
0
0.2
0.4
0.6
0.8
00.9 1.00.80.70.60.50.40.30.20.1
DIGITAL AMPLITUDE (D)
TIME (ms)
Page 11 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
CONNECTING PDM MICROPHONES
A PDM output microphone is typically connected to a codec with a dedicated PDM input. This codec separately decodes the left and right
channels and filters the high sample rate modulated data back to the audio frequency band. The codec also generates the clock for
the PDM microphones or is synchronous with the source that generates the clock.
Figure 10 and Figure 11 show mono and stereo connections between the INMP421 and a codec. The mono connection shows an
INMP421 set to output data on the right channel. To output data on the left channel, tie the L/R SELECT pin to VDD instead of GND.
Figure 10. Mono PDM Microphone (Right Channel) Connection to Codec
CLOCK OUTPUT
CODEC
0
.
1
µ
F
1
.
8
V
T
O
3
.
3
V
G
N
D
L
/
R
SE
L
E
C
T
DA
T
A
IN
M
P
4
2
1
CLK
VDD
DATA INPUT
Page 12 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
Figure 11. Stereo PDM Microphone Connection to Codec
Decouple the VDD pin of the INMP421 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 the resistor can pull the signal to an incorrect state
during the period that the signal line is tristated.
CLOCK OUTPUT
CODEC
0
.
1
µ
F
1
.
8
V
T
O
3
.
3
V
G
N
D
L
/
R
SE
L
E
C
T
DA
T
A
IN
M
P
4
2
1
CLK
VDD
DATA INPUT
0
.
1
µ
F
1
.
8
V
T
O
3
.
3
V
G
N
D
L
/
R
SE
L
E
C
T
DA
T
A
IN
M
P
4
2
1
CLK
VDD
Page 13 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
The DATA signal does not need to be buffered in normal use when the INMP421 microphones are placed close to the codec on the
PCB. If the INMP421 must drive the DATA signal over a long cable (>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 12.)
Figure 12. Buffered Connection Between Stereo INMP421 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 INMP421, 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 is turned off or the clock frequency falls below 1 kHz. In sleep mode, the
microphone data output is in high impedance state and the current consumption is less than 50 µA.
POWER SAVINGS WHEN DISABLING ONE MICROPHONE IN A MULTIMICROPHONE APPLICATION
The INMP421 has a unique power-saving feature when used in systems where two or more microphones share the same clock
and/or data lines. The microphone is designed to present high impedance on both the clock and data pins when the power supply
(VDD) pin is at 0 V or floating. This disabled microphone presents no load to and consumes no power from other active microphones.
C
L
O
C
K
O
U
T
P
U
T
C
O
D
EC
D
A
T
A
INMP421
INMP421
C
L
K
D
A
T
A
I
N
P
U
T
D
A
T
A
C
L
K
Page 14 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
SUPPORTING DOCUMENTS
For additional information, see the following documents.
EVALUATION BOARD USER GUIDE
UG-118, EVAL-INMP421Z Bottom Port Digital Output MEMS Microphone Evaluation Board
UG-326, PDM 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
Page 15 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
PCB DESIGN AND LAND PATTERN LAYOUT
Lay out the PCB land pattern for the INMP421 at a 1:1 ratio to the solder pads on the microphone package (see Figure 13.) Take care
to avoid applying solder paste to the sound hole in the PCB. Figure 14 shows a suggested solder paste stencil pattern layout.
The response of the INMP421 is not affected by the PCB hole size, as long as the hole is not smaller than the sound port of the micro-
phone (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.
Figure 13. Suggested PCB Land Pattern Layout
Dimensions shown in millimeters
Figure 14. Suggested Solder Paste Stencil Pattern Layout
Dimensions shown in millimeters
0.40 × 0.60 (4× )
(0.30)
0.90
(0.30) ø1.70
3.80
(0.30)
0.35
2.80
2× R0.10
(0.30)
0.352.05
0.70
ø1.10
(1.000)
(0.550)
CENT ER LI NE
1.45
0.9
2.45
0.7
1.525
1.000
0.35
1.849
1.849
1.498 0. 205 WI DE
0.248 × 0.498 (2× )
0.248 × 1.148 (2× )
0.248 × 0.948 (2× )
1.498 × 0.248
0.398 × 0.298 (4× )
0.362 CUT (3×)
1.17
24° 24°
0.375
CENTER
LINE
Page 16 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
ALTERNATIVE PCB LAND PATTERNS
The standard PCB land pattern of the INMP421 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 INMP421; however, it is not necessary to have the full rectangle connected for electrical functionality. If a design
can tolerate reduced RF immunity, this ring can either be broken or removed completely from the PCB footprint.
Figure 15 shows an example PCB land pattern with no enclosing rectangle around the edge of the part.
Figure 15. Example PCB Land Pattern with No Enclosing Rectangle
Figure 16 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 16. 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 15 or Figure 16 is used on a PCB, make sure that the unconnected ring on the bottom of the
INMP421 is not placed directly over any exposed copper. The rectangle 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 INMP421 is not affected by PCB thickness. The INMP421 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 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
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.
Page 18 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
OUTLINE DIMENSIONS
Figure 17. 5-Terminal Chip Array Small Outline No Lead Cavity [LGA_CAV]
4 × 3 × 1 mm Body
Dimensions shown in millimeters
Figure 18. Package Marking Specification (Top View)
04-19-2012-G
1.50
2.80
BOTTO M VI EW
TOP VIEW
SIDE VIEW
REFERENCE
CORNER
4.10
4.00
3.90
3.10
3.00
2.90
1 2 3
45
0.90
2.48
REF
0.72 REF
3.54 REF
1.05 REF
2.05
3.80
0.70
0.30 REF 0.25 DI A.
(T HRU HOLE )
1.10 DI A.
R 0.10 ( 2 ×)
1.70 DI A.
0.95 REF
0.35 0.35
0.30 REF
0.30 REF
1.10
1.00
0.90
0.24 REF
0.40 × 0. 60
(Pins 1, 2, 4, 5)
0.30 REF
PIN 1
YY XXXX
421
LOT TRACEABILITY CODE
PIN 1 INDICATION
PART NUMBER
DATE CODE
Page 19 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
ORDERING GUIDE
PART
TEMP RANGE
PACKAGE
QUANTITY
INMP421BCEZ-R0
−40°C to +85°C
5-Terminal LGA_CAV*
5,000
INMP421BCEZ-R7
−40°C to +85°C
5-Terminal LGA_CAV†
1,000
EV_INMP421-FX
—
Flexible Evaluation Board
—
EV_INMP421
—
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
Page 20 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
INMP421
Compliance Declaration Disclaimer:
InvenSense believes this compliance information to be correct but cannot guarantee accuracy or completeness. Conformity
documents for the above component constitutes 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
Environmental Declaration Disclaimer:
InvenSense believes this environmental information to be correct but cannot guarantee accuracy or completeness. Conformity
documents for the above component constitutes 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.
Page 21 of 21
Document Number: DS-INMP421-00
Revision: 1.0.
