wWM7121P, WM7121PE
Top Port Analogue Silicon Microphone
WOLFSON MICROELECTRONI CS plc Pre-Production, June 2014, Rev 3.0
Copyright 2014 Wolfson Microelectronics plc
DESCRIPTION
The WM7121P is a low-profile silicon analogue microphone.
It offers high Signal to Noise Ratio (SNR) and low power
consumption and is suited to a wide variety of consumer
applications.
The WM7121P incorporates Wolfson’s proprietary
CMOS/MEMS membrane technology, offering high reliability
and high performance in a miniature, low-profile package.
The WM7121P 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 WM7121P Top Port microphone offers matched
performance to the WM7132P Bottom Port microphone. The
matched characteristics enable highly accurate sound pick-
up in opposite directions, suitable for noise cancellation and
other DSP algorithms.
The WM7121PE 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.
FEATURES
High SNR (65dB)
Low variation in sensitivity
- ±3dB tolerance (WM7121P)
- ±1dB tolerance (WM7121PE)
Matched pair with Bottom Port microphone WM7132P
- Matched sensitivity, roll-off, and phase response
Low current consumption (190µA)
Analogue output
Top Port LGA Package
1.5V to 3.7V supply
APPLICATIONS
Mobile phone handsets
Portable media players
Digital still cameras
Digital video cameras
Bluetooth headsets
Portable navigation devices
Portable games consoles
BLOCK DIAGRAM 3D VIEW
3.76mm x 2.95mm x 1.10mm LGA package
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TABLE OF CONTENTS
DESCRIPTION ................................................................................................................ 1
FEATURES ..................................................................................................................... 1
APPLICATIONS ............................................................................................................. 1
BLOCK DIAGRAM ......................................................................................................... 1
3D VIEW ......................................................................................................................... 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
TYPICAL PERFORMANCE ............................................................................................ 6
APPLICATIONS INFORMATION ................................................................................... 7
RECOMMENDED EXTERNAL COMPONENTS ......................................................................... 7
OPTIMISED SYSTEM RF DESIGN ............................................................................................. 7
CONNECTION TO A WOLFSON CODEC .................................................................................. 8
MATCHED MICROPHONE PAIRS ............................................................................................. 8
PCB LAND PATTERN AND PASTE STENCIL ........................................................................... 9
PACKAGE DIMENSIONS ............................................................................................. 10
IMPORTANT NOTICE ............. .. .. ... .......... ... .. .. .. .. ... .. .. .. ........... .. .. .. ... .. .. .. .. .. ... ........... .. .. 11
ADDRESS: ................................................................................................................................. 11
REVISION HISTORY .................................................................................................... 12
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PIN CONFIGURATION
PIN DESCRIPTION
PIN NAME TYPE DESCRIPTION
1 VDD Supply Analogue Supply
2 GND Supply Analogue ground
3 GND Supply Analogue ground
4 OUTPUT Analogue Output Microphone analogue output signal
ORDERING INFORMATION
DEVICE DESCRIPTION
TEMPERAT URE
RANGE MOISTURE
SENSITIVITY LEVEL PEAK SOLDERING
TEMPERATURE
WM7121PIMS/RV Standard
(tape and reel) -40 to +100°C MSL2A +260°C
WM7121PIMSE/RV Enhanced
(tape and reel) -40 to +100°C MSL2A +260°C
Note:
Reel quantity = 5000
All devices are Pb-free and Halogen free.
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ABSOLUTE MAXIMUM RATINGS
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 <30°C / 85% Relative Humidity. Not normally stored in moisture barrier bag.
MSL2 = out of bag storage for 1 year at <30°C / 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 <30°C / 60% Relative Humidity. Supplied in moisture barrier bag.
The Moisture Sensitivity Level for each package type is specified in Ordering Information.
CONDITION MIN MAX
Supply Voltage (VDD) -0.3V +4.2V
Operating temperature range, TA -40°C +100°C
Storage temperature prior to soldering 30°C max / 60% RH max
Storage temperature after soldering -40°C +100°C
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.
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 a 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 SYMBOL MIN TYP MAX UNIT
Analogue Supply Range VDD 1.5 3.7 V
Ground GND 0 V
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ACOUSTIC AND ELECTRICAL CHARACTERISTICS
Test Conditions: VDD=2.1V, 1kHz test signal, TA = 25°C, unless otherwise stated.
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT
Directivity Omni-directional
Polarity Positive sound pressure Positive output voltage
Sensitivity (WM7121P) S 94dB SPL -41 -38 -35 dBV
Sensitivity (WM7121PE) S 94dB SPL -39 -38 -37 dBV
Acoustic Overload No Load, THD < 10% 126 dB SPL
Total Harmonic Distortion THD 100dB SPL 0.1 1 %
114dB SPL 0.2
122dB SPL 1
Signal to Noise Ratio SNR A-weighted 65 dB
Dynamic Range DR A-weighted 93 dB
Frequency Response -3dB low frequency 62 Hz
+3dB high frequency 15000
Frequency Response Flatness 200Hz to 6kHz -1 +1 dB
Acoustic Noise Floor A-weighted 29 dB SPL
Electrical Noise Floor A-weighted -103 dBV
Power Supply Rejection Ratio PSRR 217Hz sine wave,
100mV (peak-peak)
46 dB
Power Supply Rejection PSR 217Hz square wave,
100mV (peak-peak)
-72 dBV
Current Consumption IVDD 190 240 µA
Output DC Impedance ZOUT 55 150
TERMINOLOGY
1. Sensitivity (dBV) – Sensitivity is a measure of the microphone output response to the acoustic pressure of a 1kHz 94dB SPL
(1Pa RMS) sine wave.
2. 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 amplitude of the fundamental (ie. test frequency) output.
3. 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.
4. 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.
5. All performance measurements are carried out within a 20Hz to 20kHz bandwidth and, where noted, an A-weighted filter.
Failure to use these filters will result in higher THD and lower SNR values than are found in the Acoustic and Electrical
Characteristics. The low pass filter removes out of band noise.
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TYPICAL PERFORMANCE
Sensitivity vs. Frequency PSRR vs. Frequency
Sensitivity vs. Supply Voltage
Current Consumption vs. Suppl y Voltage
THD vs. Sound Pressure Level
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APPLICATIONS INFORMATION
RECOMMENDED EXTERNAL COMPO NENTS
Figure 1 WM7121P Recommended External Components
A DC-blocking output capacitor is required on the OUTPUT pin, as illustrated in Figure 1. A single
capacitor is required for a single-ended connection. The capacitor must be correctly selected as it
affects the cut-off frequency of the output path. A low cut-off frequency is desirable as it means there
is no significant filtering of the audio bandwidth.
The 3dB cut-off frequency of the output path is given by the equation below, where C is the output
capacitance and R is the input resistance of the other circuit.
A typical recommended configuration, with 1uF DC-blocking capacitor and 20k minimum input circuit
impedance, gives a 3dB cut-off frequency of 10Hz or less. Tantalum electrolytic capacitors are
particularly suitable for the DC-blocking components as they offer high stability in a small package
size.
OPTIMISED SYSTEM RF DESIGN
For optimised RF design please refer to document WAN0278 (Recommended PCB Layout for
Microphone RF Immunity in Mobile Cell Phone Applications) for further information.
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CONNECTION TO A WOLF SO N CODEC
Wolfson provides a range of audio CODECs incorporating an analogue microphone input interface;
these support connection to silicon microphones such as the WM7121P.
The recommended connection of a WM7121P silicon microphone is illustrated in Figure 2 (for single-
ended mode) and Figure 3 (for pseudo-differential mode).
A DC blocking capacitor is required, as described in the previous section. A 2.2µF decoupling
capacitor is also recommended; this should be positioned close to the VDD pin of the WM7121P.
Further information on Wolfson audio CODECs is provided in the respective product datasheet, which
is available from the Wolfson website.
Figure 2 WM7121P Silicon Microphone Single-ended Connection
Figure 3 WM7121P Silicon Microphone Pseudo-differential Connection
MATC HED MICRO PHONE P AI R S
The WM7121P Top Port microphone offers matched performance to the WM7132P Bottom Port
microphone. The ‘enhanced’ variants, WM7121PE and WM7132PE, offer an even greater level (±1dB)
of sensitivity performance matching.
Matched microphone pairs are ideal for accurate sound pick-up from opposite directions in slim, low-
profile applications. For best acoustic matching, the Top Port and Bottom Port microphones should be
positioned close together, on the same side of the PCB.
The WM7121P and WM7132P microphones offer matched sensitivity, low-frequency roll-off, and
phase response characteristics, enabling simplified system design when using these complementary
devices.
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PCB LAND PATTERN AND PASTE STENCIL
The recommended PCB Land Pattern and Paste Stencil Pattern for the WM7121P microphone are
shown in Figure 4 and Figure 5.
See also Application Note WAN0284 (General Design Considerations for MEMS Microphones) for
further details of PCB footprint design.
Full definition of the package dimensions is provided in the “Package Dimensions” section.
Figure 4 DM124 - PCB Land Pat tern, Top View
Figure 5 DM124 - Paste Stenctil Pattern, Top View
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PACKAGE DIMENSIONS
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IMPORTAN T NO TICE
Wolfson Microelectronics plc (“Wolfson”) products and services are sold subject to Wolfson’s terms and conditions of sale, delivery
and payment supplied at the time of order acknowledgement.
Wolfson warrants performance of its products to the specifications in effect at the date of shipment. Wolfson reserves the right to
make changes to its products and specifications or to discontinue any product or service without notice. Customers should therefore
obtain the latest version of relevant information from Wolfson to verify that the information is current.
Testing and other quality control techniques are utilised to the extent Wolfson deems necessary to support its warranty. Specific
testing of all parameters of each device is not necessarily performed unless required by law or regulation.
In order to minimise risks associated with customer applications, the customer must use adequate design and operating safeguards
to minimise inherent or procedural hazards. Wolfson is not liable for applications assistance or customer product design. The
customer is solely responsible for its selection and use of Wolfson products. Wolfson is not liable for such selection or use nor for
use of any circuitry other than circuitry entirely embodied in a Wolfson product.
Wolfson’s products are not intended for use in life support systems, appliances, nuclear systems or systems where malfunction can
reasonably be expected to result in personal injury, death or severe property or environmental damage. Any use of products by the
customer for such purposes is at the customer’s own risk.
Wolfson does not grant any licence (express or implied) under any patent right, copyright, mask work right or other intellectual
property right of Wolfson covering or relating to any combination, machine, or process in which its products or services might be or
are used. Any provision or publication of any third party’s products or services does not constitute Wolfson’s approval, licence,
warranty or endorsement thereof. Any third party trade marks contained in this document belong to the respective third party owner.
Reproduction of information from Wolfson datasheets is permissible only if reproduction is without alteration and is accompanied by
all associated copyright, proprietary and other notices (including this notice) and conditions. Wolfson is not liable for any
unauthorised alteration of such information or for any reliance placed thereon.
Any representations made, warranties given, and/or liabilities accepted by any person which differ from those contained in this
datasheet or in Wolfson’s standard terms and conditions of sale, delivery and payment are made, given and/or accepted at that
person’s own risk. Wolfson is not liable for any such representations, warranties or liabilities or for any reliance placed thereon by
any person.
ADDRESS:
Wolfson Microelectronics plc
Westfield House
26 Westfield Road
Edinburgh
EH11 2QB
Tel :: +44 (0)131 272 7000
Fax :: +44 (0)131 272 7001
Email :: sales@wolfsonmicro.com
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REVISION HISTORY
DATE REV DESCRIPTION OF CHANGES PAGE CHANGED BY
26/02/14 1.0 First Release IS
25/03/14 2.0 Formatting and miscellaneous updates throughout document
Electrical Characteristics updated
Package Outline Drawing updated
1-9
5
10
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13/06/14 3.0 Electrical Characteristics updated
Typical Performance graphs added
PCB Stencil drawings updated
Package Outline Drawing updated
5
6
9
10
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