ANALOG DEVICES ADMP421 Service Manual
Bottom Port and Digital Output
ADMP421
Rev. D
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ADMP421
ADC
POWER
MANAGEMENT
CLK
DATA
VDD
GND
PDM
MODULATOR
CHANNEL
SELECT
L/R SELECT
07596-001
Data Sheet
FEATURES
Small and thin 3 mm × 4 mm × 1 mm surface-mount package
High SNR of 61 dBA
High 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
APPLICATIONS
Smartphones and feature phones
Teleconferencing systems
Digital video cameras
Bluetooth headsets
Video phones
Tablets
Omnidirectional Microphone with
GENERAL DESCRIPTION
The ADMP421 is a high performance, low power, digital output
bottom-ported omnidirectional MEMS microphone. The
ADMP421 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 timemultiplexed on a single data line using a single clock.
The ADMP421 has a high SNR and high sensitivity, making it
an excellent choice for far field applications. The ADMP421 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 builtin particle filter provides high reliability. The ADMP421 complies
with the TIA-920 Telecommunications Telephone Terminal
Equipment Transmission Requirements for Wideband Digital
Wireline Telephones standard.
The ADMP421 is available in a thin 3 mm × 4 mm × 1 mm
surface-mount package. It is reflow solder compatible with no
sensitivity degradation. The ADMP421 is halide free.
FUNCTIONAL BLOCK DIAGRAM
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Figure 1.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
ADMP421 Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Timing Characteristics ................................................................ 4
Absolute Maximum Ratings ............................................................ 5
ESD Caution .................................................................................. 5
Pin Configuration and Function Descriptions ............................. 6
Typical Performance Characteristics ............................................. 7
PCB Land Pattern Layout ................................................................ 8
Alternate PCB Land Patterns ...................................................... 9
REVISION HISTORY
11/11—Rev. C to Rev. D
Changed PSRR to PSR ....................................................... Universal
Changed Pb-Free Temperature from 245°C to 260°C, Table 4 .. 5
Changes to Figure 8 and Figure 9 ................................................... 8
Added Alternate PCB Land Patterns Section ............................... 9
Changes to Temperature Humidity Bias (THB) Description,
Table 6 .............................................................................................. 12
8/11—Rev. B to Rev. C
Changes to Clock Frequency and Supply Voltage Parameters,
Table 1 ................................................................................................ 3
Changes to Table 3 and Table 4 ....................................................... 5
Deleted Power-Saving Features Section ........................................ 8
Changes to Figure 9 .......................................................................... 8
Added Applications Information Section ..................................... 9
Added Supporting Documents, Evaluation Board User Guides,
Circuit Note, and Application Notes Sections .............................. 9
Changes to Interfacing with Analog Devices Codecs
Section ................................................................................................ 9
Moved Sleep Mode Section and Power Savings When Disabling
One Microphone in a Multimicrophone Application Section ... 9
Changes to Figure 10 ........................................................................ 9
Change to Pick-and-Place Equipment Section ........................... 10
Deleted Evaluation Board Section ................................................ 10
Deleted Figure 10 and Figure 11; Renumbered Sequentially ... 10
Deleted Table 6; Renumbered Sequentially................................. 10
Deleted Figure 12 ............................................................................ 11
Change to Temperature Cycle Description, Table 6 .................. 11
Changes to Ordering Guide .......................................................... 12
Applications Information .............................................................. 10
Interfacing with Analog Devices Codecs ................................ 10
Sleep Mode .................................................................................. 10
Power Savings When Disabling One Microphone in a
Multimicrophone Application .................................................. 10
Supporting Documents ............................................................. 10
Handling Instructions .................................................................... 11
Pick-and-Place Equipment ....................................................... 11
Reflow Solder .............................................................................. 11
Board Wash ................................................................................. 11
Reliability Specifications ................................................................ 12
Outline Dimensions ....................................................................... 13
Ordering Guide .......................................................................... 13
6/11—Rev. A to Rev. B
Changes to Figure 1 ........................................................................... 1
Changes to Figure 5 ........................................................................... 7
2/11—Rev. 0 to Rev. A
Changes to Features Section, Applications Section, and
General Description Section ............................................................ 1
Added Dynamic Range Parameter, Changes to Input
Characteristics Parameter and Output Characteristics
Parameter, Deleted Polarity Parameter, Table 1 ............................ 3
Changes to Table 3 ............................................................................. 5
Changes to Table 5 ............................................................................. 6
Added Power-Saving Features Section ........................................... 8
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 13
4/10—Revision 0: Initial Version
Rev. D | Page 2 of 16
Data Sheet ADMP421
PERFORMANCE
Dynamic Range
Derived from EIN and maximum acoustic input
87 dB
Power Supply Rejection
PSR
217 Hz, 100 mV p-p square wave
80 dBFS
Output Voltage Low
VOL
I
= 0.5 mA
0 0.3 × VDD
V
SPECIFICATIONS
TA = 25°C, VDD = 1.8 V, CLK = 2.4 MHz, unless otherwise noted. All minimum and maximum specifications are guaranteed. Typical
specifications are not guaranteed.
Table 1.
Parameter Symbol Test Conditions/Comments Min Typ Max Unit
Directionality Omni
Sensitivity1 1 kHz, 94 dB SPL −29 −26 −23 dBFS
Signal-to-Noise Ratio SNR 20 kHz bandwidth, A-weighted 61 dBA
Equivalent Input Noise EIN 20 kHz bandwidth, A-weighted 33 dBA SPL
Frequency Response2 Low frequency −3 dB point 100 Hz
High frequency −3 dB point 15 kHz
Deviation limits from flat response within
pass band
Total Harmonic Distortion THD 105 dB SPL 3 %
superimposed on VDD = 1.8 V
Maximum Acoustic Input Peak 120 dB SPL
INPUT CHARACTERISTICS
Clock Frequency CLK 1.0 2.43 3.3 MHz
Clock Duty Ratio Clock frequency of 2.4 MHz or less 40 60 %
Input Voltage High VIH 0.65 × VDD V
Input Voltage Low VIL 0.35 × VDD V
OUTPUT CHARACTERISTICS
Output Voltage High VOH I
= 0.5 mA 0.7 × VDD VDD V
LOAD
LOAD
Latency <30 µs
Wake-Up Time From sleep mode, power on 10 ms
POWER SUPPLY
Supply Voltage VDD 1.8 3.3 V
Supply Current IS Normal mode 650 µA
Sleep mode4 50 µA
1
Relative to the rms level of a sine wave with positive amplitude equal to 100% 1s density and negative amplitude equal to 0% 1s density.
2
See Figure 5 and Figure 6.
3
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.
4
The microphone enters sleep mode when the clock is turned off or the clock frequency is less than 1 kHz.
−3/+2 dB
Rev. D | Page 3 of 16
ADMP421 Data Sheet
TIMING CHARACTERISTICS
Table 2.
Parameter Description Min Max Unit
Input
t
Input clock period 310 1000 ns
CLKIN
Output
t
DATA1 driven after falling clock edge 30 ns
1OUTEN
t
DATA1 disabled after rising clock edge 20 ns
1OUTDIS
t
DATA2 driven after rising clock edge 30 ns
2OUTEN
t
DATA2 disabled after falling clock edge 20 ns
2OUTDIS
Timing Diagram
t
CLKIN
CLK
DATA1
DATA2
t
2OUTEN
t
1OUTEN
t
2OUTDIS
t
1OUTDIS
07596-002
Figure 2. Pulse Density Modulated Output Timing
Rev. D | Page 4 of 16
Data Sheet ADMP421
A
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
Supply Voltage −0.3 V to 3.6 V
Digital Pin Input Voltage
−0.3 V to V
+ 0.3 V or 3.6 V,
DD
whichever is less
Sound Pressure Level (SPL) 160 dB
Mechanical Shock 10,000 g
Vibration
Per MIL-STD-883 Method 2007,
Test Condition B
Temperature Range −40°C to +85°C
T
P
T
L
T
SMAX
TURE
T
SMIN
TEMPER
t
S
PREHEAT
RAMP-UP
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
t
P
RAMP-DOWN
CRITICAL ZONE
t
L
T
TO T
L
P
t
25°C TO PEAK
TIME
07596-003
Figure 3. Recommended Soldering Profile Limits
Table 4. Recommended Soldering Profile Limits
Profile Feature Sn63/Pb37 Pb Free
Average Ramp Rate (TL to TP) 1.25°C/sec max 1.25°C/sec max
Preheat
Minimum Temperature (T
Maximum Temperature (T
Time (T
Ramp-Up Rate (T
SMIN
to T
), tS 60 sec to 75 sec 60 sec to 75 sec
SMAX
to TL) 1.25°C/sec 1.25°C/sec
SMAX
) 100°C 100°C
SMIN
) 150°C 200°C
SMAX
Time Maintained Above Liquidous (tL) 45 sec to 75 sec ~50 sec
Liquidous Temperature (TL) 183°C 217°C
Peak Temperature (TP) 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 (t25°C) to Peak Temperature 5 minute max 5 minute max
Rev. D | Page 5 of 16
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