EV_INMP421

INMP421 Omnidirectional Microphone with Bottom Port and PDM Digital Output GENERAL DESCRIPTION APPLICATIONS 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 timemultiplexed 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 surfacemount package. It is reflow solder compatible with no sensitivity degradation. The INMP421 is halide free.        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: 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.) INMP421 CODEC CLOCK OUTPUT CLK DATA DATA INPUT INMP421 CLK DATA 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 12. 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. Page 14 of 21 Document Number: DS-INMP421-00 Revision: 1.1 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: 1.1 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 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 Figure 13. Suggested PCB Land Pattern Layout Dimensions shown in millimeters 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×) Figure 14. Suggested Solder Paste Stencil Pattern Layout Dimensions shown in millimeters Page 16 of 21 Document Number: DS-INMP421-00 Revision: 1.1 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 rectangle 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 rectangle 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: 1.1 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: 1.1 INMP421 OUTLINE DIMENSIONS 4.10 4.00 3.90 0.95 REF 2.05 1.70 DIA. REFERENCE CORNER 3.54 REF 0.70 0.40 × 0.60 (Pins 1, 2, 4, 5) PIN 1 0.30 REF 0.90 2.48 REF 3 1 2 5 4 0.30 REF 3.10 3.00 2.90 1.10 DIA. 1.50 0.25 DIA. (THRU HOLE) R 0.10 (2 ×) TOP VIEW 0.35 1.10 1.00 0.90 2.80 1.05 REF 0.35 0.30 REF 0.30 REF 0.72 REF SIDE VIEW 04-19-2012-G 3.80 BOTTOM VIEW 0.24 REF Figure 17. 5-Terminal Chip Array Small Outline No Lead Cavity [LGA_CAV] 4 × 3 × 1 mm Body Dimensions shown in millimeters PART NUMBER DATE CODE PIN 1 INDICATION LOT TRACEABILITY CODE Figure 18. Package Marking Specification (Top View) Page 19 of 21 Document Number: DS-INMP421-00 Revision: 1.1 INMP421 ORDERING GUIDE PART INMP421BCEZ-R0 TEMP RANGE −40°C to +85°C PACKAGE 5-Terminal LGA_CAV* QUANTITY 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 05/21/2014 1.1 Updated Compliance Disclaimer Page 20 of 21 Document Number: DS-INMP421-00 Revision: 1.1 INMP421 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. Page 21 of 21 Document Number: DS-INMP421-00 Revision: 1.1