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DESCRIPTION
The WM7220 is a low-profile silicon digital microphone. It
offers high Signal to Noise Ratio (SNR) and low power
consumption and is suited to a wide variety of consumer
applications.
The WM7220 incorporates Wolfson’s proprietary
CMOS/MEMS membrane technology, offering high
reliability and high performance in a miniature, low-profile
package. The WM7220 is designed to withstand the high
temperatures associated with automated flow solder
assembly processes. (Note that conventional microphones
can be damaged by this process.)
The WM7220 incorporates a high performance ADC,
which outputs a single-bit Pulse Density Modulated (PDM)
audio data stream. The WM7220 supports selectable
left/right channel assignment for a two-channel digital
microphone interface, enabling efficient connection of
multiple microphones in stereo/array configurations.
The WM7220E variant offers a tighter tolerance on the
microphone sensitivity, giving reduced variation between
parts. This removes the need for in-line production
calibration of part-to-part microphone variations.
-
-
-
-
WM7220, WM7220E
Top Port Digital Silicon Microphone
FEATURES
High SNR; selectable sensitivity tolerance options
WM7220 – SNR 58dB, Sensitivity +/- 3dB
WM7220E – SNR 58dB, Sensitivity +/- 1dB
Sleep mode - 2μA
Normal operation - 700μA
Low power
Low profile packaging
Support for automated flow solder assembly
PDM digital audio output
Stereo/array operation
Proprietary ADC technology
-
-
-
Reduced clock jitter sensitivity
Low noise floor modulation
Stable in overload condition
Top port package
1.64V to 3.7V supply
4.72 x 3.76 x 1.22mm thin package design
APPLICATIONS
Mobile telephone handsets
Portable computers
Portable media players
Digital still cameras
Digital video cameras
Bluetooth headsets
Portable navigation devices
BLOCK DIAGRAM
WOLFSON MICROELECTRONICS plc
Pre-Production, December 2012, Rev 3.2
Copyright
2012
Wolfson Microelectronics plc
WM7220
TABLE OF CONTENTS
Pre-Production
DESCRIPTION ....................................................................................................... 1
FEATURES ............................................................................................................ 1
APPLICATIONS..................................................................................................... 1
BLOCK DIAGRAM ................................................................................................ 1
TABLE OF CONTENTS ......................................................................................... 2
PIN CONFIGURATION .......................................................................................... 3
PIN DESCRIPTION ................................................................................................ 3
ORDERING INFORMATION .................................................................................. 3
ABSOLUTE MAXIMUM RATINGS ........................................................................ 4
IMPORTANT ASSEMBLY GUIDELINES .............................................................. 4
RECOMMENDED OPERATING CONDITIONS ..................................................... 4
ACOUSTIC AND ELECTRICAL CHARACTERISTICS ......................................... 5
TERMINOLOGY ............................................................................................................... 5
AUDIO INTERFACE TIMING ........................................................................................... 6
TYPICAL PERFORMANCE ................................................................................... 7
FREQUENCY RESPONSE .............................................................................................. 7
THD RATIO ...................................................................................................................... 7
APPLICATIONS INFORMATION .......................................................................... 8
RECOMMENDED EXTERNAL COMPONENTS .............................................................. 8
OPTIMISED SYSTEM RF DESIGN ................................................................................. 8
CONNECTION TO A WOLFSON AUDIO CODEC .......................................................... 8
RECOMMENDED PCB LAND PATTERNS ..................................................................... 9
PACKAGE DIMENSIONS (LGA) ......................................................................... 10
IMPORTANT NOTICE ......................................................................................... 11
ADDRESS: .......................................................................................................... 11
REVISION HISTORY ........................................................................................... 12
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WM7220
PIN CONFIGURATION
1
2
3
6
5
4
Top View
PIN DESCRIPTION
PIN
1
2
NAME
GND
LRSEL
TYPE
Supply
Digital Input
Ground
Channel Select
DESCRIPTION
0 = Data output following falling CLK edge
1 = Data output following rising CLK edge
3
4
5
6
GND
CLK
DAT
VDD
Supply
Digital Input
Digital Output
Supply
Ground
Clock input
PDM Data Output
Power Supply
ORDERING INFORMATION
DEVICE
WM7220IMS/V
WM7220IMS/RV
WM7220IMSE/V
WM7220IMSE/RV
Note:
Reel quantity = 4800
All devices are Pb-free and Halogen free.
DESCRIPTION
Standard
Standard
(tape and reel)
Standard Enhanced
Standard Enhanced
(tape and reel)
TEMPERATURE
RANGE
-40 to +100 C
-40 to +100 C
-40 to +100 C
-40 to +100 C
o
o
o
o
MOISTURE
SENSITIVITY LEVEL
MSL2A
MSL2A
MSL2A
MSL2A
PEAK SOLDERING
TEMPERATURE
+260 C
+260 C
+260 C
+260 C
o
o
o
o
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WM7220
ABSOLUTE MAXIMUM RATINGS
Pre-Production
Absolute Maximum Ratings are stress ratings only. Permanent damage to the device may be caused by continuously operating at
or beyond these limits. Device functional operating limits and guaranteed performance specifications are given under Electrical
Characteristics at the test conditions specified.
ESD Sensitive Device. This device is manufactured on a CMOS process. It is therefore generically susceptible
to damage from excessive static voltages. Proper ESD precautions must be taken during handling and storage
of this device.
Wolfson tests its package types according to IPC/JEDEC J-STD-020 for Moisture Sensitivity to determine acceptable storage
conditions prior to surface mount assembly. These levels are:
MSL1 = unlimited floor life at <30C / 85% Relative Humidity. Not normally stored in moisture barrier bag.
MSL2 = out of bag storage for 1 year at <30C / 60% Relative Humidity. Supplied in moisture barrier bag.
MSL2A = out of bag storage for 4 weeks at <30°C / 60% Relative Humidity. Supplied in moisture barrier bag.
MSL3 = out of bag storage for 168 hours at <30C / 60% Relative Humidity. Supplied in moisture barrier bag.
The Moisture Sensitivity Level for each package type is specified in Ordering Information.
CONDITION
Supply Voltage (VDD)
Voltage range digital inputs (LRSEL and CLK)
Operating temperature range, T
A
Storage temperature prior to soldering
Storage temperature after soldering
MIN
-0.3V
GND-0.3V
-40ºC
MAX
+4.2V
VDD + 0.3V
+100ºC
30C max / 60% RH max
-40ºC
+100ºC
IMPORTANT ASSEMBLY GUIDELINES
Do not put a vacuum over the port hole of the microphone. Placing a vacuum over the port hole can damage the device. For
information on recommended pick and place vacuum point, refer to the package dimension drawing.
Do not board wash the microphone after a re-flow process. Board washing and the associated cleaning agents can damage
the device. Do not expose to ultrasonic cleaning methods.
Do not use vapour phase re-flow process. The vapour can damage the device.
Please refer to application note WAN0273 (MEMS MIC Assembly and Handling Guidelines) for further assembly and
handling guidelines.
RECOMMENDED OPERATING CONDITIONS
PARAMETER
Analogue Supply Range
Ground
Clock Frequency
SYMBOL
VDD
GND
F
CLK
MIN
1.64
TYP
0
MAX
3.7
3.25
UNIT
V
V
MHz
1
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WM7220
ACOUSTIC AND ELECTRICAL CHARACTERISTICS
Test Conditions:
VDD=1.8V, 1kHz test signal, CLK=2.4MHz, T
A
= 25°C
PARAMETER
Directivity
Sensitivity (WM7220)
Sensitivity (WM7220E)
Acoustic Overload
Signal to Noise Ratio
Total Harmonic Distortion
Dynamic Range
Frequency Response
Acoustic Noise Floor
Electrical Noise Floor
Power Supply Rejection
Digital Input / Output
CLK Input HIGH Level
CLK Input LOW Level
DAT Output HIGH Level
DAT Output LOW Level
Input capacitance (CLK)
Maximum load capacitance
(DAT)
Input Leakage
Short Circuit Output Current
Miscellaneous
Current Consumption
Start-up Time
CLK Sleep Frequency
SYMBOL
S
S
SNR
THD
DR
TEST CONDITIONS
94 dB SPL
94 dB SPL
THD < 10%
A-Weighted
100dB SPL
A-weighted noise floor to 1%
THD
-3dB Low frequency
+3dB High frequency
A-weighted
A-weighted
MIN
-29
-27
TYP
Omni-directional
-26
-26
120
58
0.1
81
35
9000
36
-84
-65
MAX
-23
-25
UNIT
dBFS
dBFS
dB SPL
dB
1
%
dB
Hz
Hz
dB SPL
dBFS
dBFS
PSR
217Hz Square Wave
100mV pk-pk
V
IH
V
IL
V
OH
V
OL
C
IN
C
LOAD
I
OH
= +1mA
I
OL
= -1mA
0.65 x
VDD
0.35 x
VDD
0.9 x
VDD
0.1 x
VDD
0.5
100
1
V
V
V
V
pF
pF
μA
mA
μA
10
ms
1.0
kHz
I
SC
I
VDD
DAT connected to GND
Active Mode
SLEEP Mode
From OFF
From SLEEP
700
2
10
10
10
TERMINOLOGY
1.
2.
Sensitivity (dBFS) - Sensitivity is a measure of the microphone output response to the acoustic pressure of a 1kHz
94dB SPL (1Pa RMS) sine wave. This is referenced to the output Full Scale Range (FSR) of the microphone.
Full Scale Range (FSR) - Sensitivity, Electrical Noise Floor and Power Supply Rejection are measured with reference
to the output Full Scale Range (FSR) of the microphone. FSR is defined as the amplitude of a 1kHz sine wave output
whose positive peak value reaches 100% density of logic 1s and whose negative peak value reaches 0% density of
logic 1s. This is the largest undistorted 1kHz sine wave that will fit in the digital output numerical range. Note that,
because the definition of FSR is based on a sine wave, it is possible to support a square wave test signal output
whose level is +3dBFS.
Signal-to-Noise Ratio (dB) – SNR is a measure of the difference in level between the output response of a 1kHz 94dB
SPL sine wave and the idle noise output.
Total Harmonic Distortion (%) – THD is the ratio of the RMS sum of the harmonic distortion products in the specified
bandwidth (see note below) relative to the RMS amplitude of the fundamental (ie. test frequency) output.
Dynamic Range (dB) - DR is the ratio of the 1% THD microphone output level (in response to a sine wave input) and
the idle noise output level. Parameter validated in electroacoustic laboratory and not guaranteed.
3.
4.
5.
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