CDB7236 Customer Demo Board for the WM7236 Features Description • WM7236 MEMS microphone The CDB7236 is a flexible PCB for full electrical and acoustic validation of the WM7236 MEMS microphone. The CDB7236 is designed to connect to test equipment via on board test points or via a codec main board with mating edge connector socket. • Flexible PCB for full acoustic validation — Pressure Field — Free Field The CDB7236 is ideally suited for pressure field acoustic measurements. Furthermore, the flexible region can be trimmed to enable accurate free field measurements to be made. • Plug and play interface to smart codec main board — Functional test — Full signal path setup with smart codec The CDB7236 also serves as a component and layout reference for the WM7236. — System development and prototyping — Algorithm verification Ordering Information CDBWM7236-M-2 Customer Demo Board Acoustic port hole WM7236 Power and I/O T ri m lin e Test points Power and I/O Edge connector pads http://www.cirrus.com Copyright Cirrus Logic, Inc. 2015 (All Rights Reserved) DS1128DB1 DEC '15 CDB7236 Table of Contents 1 System Overview .......................................................................................................................................................... 3 1.1 Test Points ............................................................................................................................................................. 3 1.2 Edge Connector ..................................................................................................................................................... 3 1.3 Trim Line ................................................................................................................................................................ 3 2 Quick Setup Guide ........................................................................................................................................................ 4 2.1 Pressure field acoustic test .................................................................................................................................... 4 2.2 Free field acoustic test ........................................................................................................................................... 5 3 Schematic ...................................................................................................................................................................... 6 4 Layout ............................................................................................................................................................................ 7 5 Known Issues ................................................................................................................................................................ 7 6 Bill of Materials ............................................................................................................................................................. 8 7 Revision History ........................................................................................................................................................... 8 2 DS1128DB1 CDB7236 1 System Overview 1 System Overview The CDB7236 customer demo board is a flexible PCB for evaluating the WM7236 low-profile always-on digital silicon microphone. The following subsections describe the features of CDB7236 customer demo board in detail. 1.1 Test Points Test points are available to provide all the connections from WM7236 to standard test equipment for full acoustic measurement. Test points are described in Table 1-1. The operating supply voltage of WM7236 is provided in the data sheet, which is available from Cirrus website. Table 1-1. Test Point signals Test Point TP1, TP5, TP6, TP8 TP2, TP11 TP3, TP10 TP4, TP7 TP9 Pin GND VDD DAT CLK LRSEL Direction Ground reference Supply Digital output Digital input Digital input Description Ground Power supply PDM data output Clock input Channel select 0 = Data output following falling CLK edge 1 = Data output following rising CLK edge Internal pull-down holds this pin at Logic 0 when not connected 1.2 Edge Connector The J1 and J2 edge connector pads provide a pluggable connection to a codec main board with compatible edge card socket. The edge connector pin-outs are described in Table 1-2 and Table 1-3. Table 1-2. Edge connection J1 Pin Pin Direction 1 NC — 2 3 4 5 6 7, 8, 9, 10 VDD GND CLK DAT LRSEL NC Supply Ground reference Digital input Digital output Digital input — Description No connection (pin 1 is marked by a small dot) Power supply from codec MICBIAS Ground Clock input PDM data output Channel select No connection Table 1-3. Edge connection J2 Pin 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Pin NC Direction N/A Description No Connection 1.3 Trim Line To enable more accurate free field frequency responses to be obtained, the flexible region of the CDB7236 may be trimmed to reduce acoustic interactions. If required, there is a guide line on the silkscreen that can be cut along. Refer to Fig. 4-1 for further details. 3 DS1128DB1 CDB7236 2 Quick Setup Guide 2 Quick Setup Guide As a standalone PCB, the CDB7236 can be used in a pressure field acoustic test setup or free field acoustic test setup. It can also be connected to a compatible codec main board to enable full signal path setup within a system platform. Acoustic measurements can be obtained using a number of different methods. Typical acoustic test setups, using a comparison method, are shown in Section 2.1 and Section 2.2. 2.1 Pressure field acoustic test Recommendations for accurate pressure field measurements are as follows: • Ensure calibrated test equipment is used for making measurements • Ensure CDB7236 acoustic port hole is tightly sealed within the pressure field test cavity • Ensure CDB7236 and reference mic are placed close together with minimum placement error • Use a suitable test microphone—a pressure field reference microphone is recommended • Ensure the pressure field test cavity is tightly sealed • Measurements should be performed within a quiet environment Quiet Environment Pressure Field Test Cavity Power CDB7236 Test Speaker Sound Pressure Level Test Point Connections Pressure Field Reference Mic Standard Test Equipment Figure 2-1. Pressure field test setup with CDB7236 4 DS1128DB1 CDB7236 2.2 Free field acoustic test 2.2 Free field acoustic test Recommendations for accurate free field measurements are as follows: • Ensure calibrated test equipment is used for making measurements • Ensure CDB7236 acoustic port hole and reference mic are facing to the incoming sound pressure • Ensure CDB7236 and reference mic are placed close together with minimum placement error • The CDB7236 may be trimmed along the ‘Trim line’ to improve accuracy • Use a suitable test microphone—a free field reference microphone is recommended • Measurements should be performed within an anechoic environment Anechoic Chamber Power CDB7236 Test Speaker Sound Pressure Level Test Point Connections Free Field Reference Mic Standard Test Equipment Figure 2-2. Free field test setup with CDB7236 5 DS1128DB1 CDB7236 3 Schematic 3 Schematic TP1 MICROPHONE CIRCUIT GND Pads on flex VDD DUTVDD R3 0R TP2 TP3 R1 0R Unpop U1 3 VDD DAT LRSEL C2 1uF Unpop 1 C1 0.1uF CLK GND 2 DAT 5 LRSEL 4 TP5 TP4 GND GND R2 0R GND GND CLK VDD CLK DAT LR TP11 TP7 TP10 TP9 VDD J1 1 2 3 4 5 6 7 8 9 10 J2 1 1 2 2 3 3 4 5 6 CLK 4 DAT 5 LRSEL 6 7 8 GND 9 TP6 7 8 9 10 10 1 2 3 4 5 6 7 8 9 10 TP8 CON_FING_10WAY_0.8PITCH_A CON_FING_10WAY_0.8PITCH_B GND GND 6 DS1128DB1 CDB7236 4 Layout 4 Layout Figure 4-1. Flex Top Layer + Silkscreen Figure 4-2. Flex Bottom Layer Figure 4-3. PCB Top Layer Figure 4-4. PCB Bottom Layer + Silkscreen 5 Known Issues There are no known issues with this board. 7 DS1128DB1 CDB7236 6 Bill of Materials 6 Bill of Materials Table 6-1. Bill of Materials Item 1 2 3 4 5 6 7 RefDes PCB1 U1 C1 R1 R2 C2 [1] R3 [1] Description Printed circuit board WM7236 bottom port digital silicon microphone 0.1-F 0603 SMD ceramic capacitor 16 V X7R 0- 0603 SMD chip resistor 1% 0.063 W 0- 0603 SMD chip resistor 1% 0.063 W 1-F 0603 SMD ceramic capacitor 16 V X7R 0- 0603 SMD chip resistor 1% 0.063 W Manufacturer Cirrus Logic Cirrus Logic Phycomp Multicomp Multicomp Phycomp Multicomp Manufacturer's Part Number CDB72B-5A-M1-REV1 WM7236IMSE/V 2238 786 15649 MC 0.063W 0603 0R MC 0.063W 0603 0R 225524615663 MC 0.063W 0603 0R 1.These items are unpopulated by default on the CDBWM7236-M-2 customer demo board. 7 Revision History Table 7-1. Revision History Release Changes DB1 Initial revision DEC ‘15 Important: Please check www.Cirrus.com to confirm that you are using the latest revision of this document and to determine whether there are errata associated with this device. Contacting Cirrus Logic Support For all product questions and inquiries, contact a Cirrus Logic Sales Representative. To find the one nearest you, go to www.cirrus.com. IMPORTANT NOTICE The products and services of Cirrus Logic International (UK) Limited; Cirrus Logic, Inc.; and other companies in the Cirrus Logic group (collectively either “Cirrus Logic” or “Cirrus”) are sold subject to Cirrus Logic’s terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. Software is provided pursuant to applicable license terms. Cirrus Logic 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 Cirrus Logic to verify that the information is current and complete. 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