UG395: WFM200 Hardware Design User's Guide This document provides information to help users design Wi-Fi applications using the WFM200. KEY FEATURES • Schematics guidelines • BOM selection guideline • Antenna matching guideline • Layout guideline • Package information • Certification guideline silabs.com | Building a more connected world. This information applies to a product under development. Its characteristics and specifications are subject to change without notice. Preliminary Rev. 0.
Table of Contents 1. WFM200 Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Device Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Features Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 WFM200 RF Ports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Host Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.3 Programmable Pins . . . . . .
UG395: WFM200 Hardware Design User's Guide WFM200 Pinout 1. WFM200 Pinout WFM200 is a 6.5 x 6.5 mm LGA module. The diagram below describes the pinout (top view). Figure 1.1. WFM200 Pinout Table 1.1. WFM200 Pin Description Pin # WFM200 Pin Name 1 GND 2 Description 2G4ANT_IN, or No Connect on OPN Embedded 2.4 GHz antenna port. To use the antenna, connect this pin to with no integral antenna RF_1.
UG395: WFM200 Hardware Design User's Guide WFM200 Pinout Pin # WFM200 Pin Name Description 18 LP_CLK Low Power clock input. This pin is typically connected to the 32 kHz clock. If not used, the pin should be connected to GND. 19 GPIO/WIRQ 20 VDD 21 GND 22 SDIO_CLK/SPI_CLK 23 SDIO_CMD/SPI_MOSI Host interface: SDIO_CMD or SPI_MOSI. 24 SDIO_DAT0/SPI_MISO Host interface: SDIO_DAT0 or SPI_MISO. 25 SDIO_DAT1/SPI_WIRQ Host interface: SDIO_DAT1 or WIRQ.
UG395: WFM200 Hardware Design User's Guide Device Configuration 2. Device Configuration The configuration linked to the hardware platform (RF pins, configurable pins, etc.) is achieved through firmware by downloading a dedicated binary file (a PDS file, which stands for "Platform Data Set") just after firmware download and before operation. More details on device configuration will be provided in an upcoming application note. Table 2.1.
UG395: WFM200 Hardware Design User's Guide Features Description 3. Features Description 3.1 WFM200 RF Ports WFM200 has two Tx/Rx RF ports named RF_1 (pin 3) and RF_2 (pin 9). RF_1 and RF_2 have internal low-pass filtering and RF impedance matching components to 50 Ω in the 2.4 GHz band of operation. Any of the RF ports can be used in a similar way. However, note that RF_2 output power is around 1 dB lower than that of RF_1.
UG395: WFM200 Hardware Design User's Guide Features Description 3.2 Host Interface The host interface allows control of the WFM200 by an MCU or SoC using either SPI or SDIO. Selection between SPI and SDIO is done upon the logic state on the SDIO_DAT2/HIF_SEL pin during the rising edge of the RESETn signal. If this signal is HIGH, the host interface is configured as SDIO; otherwise, it is configured as SPI. These configurations are summarized in the table below: Table 3.1.
UG395: WFM200 Hardware Design User's Guide Features Description 3.3 Programmable Pins 3.3.1 Multi-Protocol Coexistence If an RF transceiver using the same 2.4 GHz band (e.g., Bluetooth, Zigbee, or Thread) is located next to the WFM200 Wi-Fi transceiver, a Packet Transfer Arbitration (PTA) interface can be used to minimize mutual interference. In this case, PTA pins are connected to the other transceiver. The PTA interface is highly programmable and can use 1, 2, 3, or 4 pins upon configuration.
UG395: WFM200 Hardware Design User's Guide Power Supplies 4. Power Supplies WFM200 has three power supply pins. • VDD_PA supplies the Power amplifier. Recommended to have VDD_PA as the highest supply voltage of WFM200. • VDD supplies the core, i.e., both RF and digital parts. • VDD_IO supplies the pins and determines the voltage levels on pins, so this voltage should be compatible with WFM200 peripherals. Bypass capacitors and filtering are included internally.
UG395: WFM200 Hardware Design User's Guide Application Schematic Recommendations 5. Application Schematic Recommendations 5.1 Power Supplies – Schematics Care should be taken that the VDD_PA supply source is capable of supplying enough current for the load peaks of the power amplifier (which can go momentarily up to 200 mA), so it is recommended to select a regulator capable of supplying 300 mA.
UG395: WFM200 Hardware Design User's Guide Typical Application Schematics 6. Typical Application Schematics The following diagrams show simple applications using SDIO and SPI interfaces. Figure 6.1. Application Using SDIO Interface silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Typical Application Schematics Figure 6.2. Application Using SPI Interface silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7. Layout Recommendations The figure below shows the WFM200 section of Silicon Labs’ reference board layout with some feature highlights. Figure 7.1. WFM200 Portion of Reference Design Board Layout silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.1 Generic RF Layout Considerations For custom designs, use the same number of PCB layers as are present in the reference design. Deviation from the reference PCB layer count can cause different PCB parasitic capacitances, which can detune the antenna matching network from its optimal form.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations Figure 7.2. Reference Design PCB Specification silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.2 GND and RF Pads Including the Diversity Port and External Antennas WFM200 ground pads need to be well connected to the PCB ground plane to optimize thermal conductivity and prevent unwanted emissions that result from ground currents. The RF pads and RF traces conducting the RF signal should be dimensioned to have a characteristic impedance of 50 Ω.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3 Module Antenna To minimize impedance detuning and degradation of the radiation pattern, reduce as much shielding of the selected antenna as possible. The ground plane usually forms an important part of the antenna as there is significant current running along the ground plane (i.e., the GND plane is also part of any monopole-type antenna, in general).
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3.1 Small Board Size Recommendations for Good RF Performance Figure 7.4. Reference Design for Small PCB Sizes Note: Spaces filled in black represent metal keep-outs on the PCB in the figure above. • • • • • • • • • • • • Required WFM200 Board size in X = 17.5 mm ± 3 mm of metal. Required WFM200 Board size in Y = 55 mm ± 3 mm of metal. PCB may be slightly larger to account for PCB edge routing. Area for optimum performance is 55 mm z 17.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3.2 Extended X Dimension Recommendation for Good RF Performance Figure 7.5. Reference Design for Extended X-dimensioned PCB Sizes* Note: Spaces filled in black represent metal keep-outs on the PCB in the figure above.* • • • • • • • • • • • Required WFM200 portion size is X = 17.5 mm of metal. Required board size is Y = 55mm ± 3 mm of metal. PCB may be slightly larger to account for PCB edge routing.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3.3 Y Dimension (65 to 80 mm) Recommendation for Good RF Performance Figure 7.6. Reference Design for Extended X- and Slightly Extended Y-dimensioned PCB Sizes* Note: Spaces filled in black represent metal keep-outs on the PCB in the figure above.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3.4 Y Dimension (80 mm or Larger) Recommendation for Good RF Performance Figure 7.7. Reference Design for Extended X- and Y-dimensioned PCB Sizes* Note: Spaces filled in black represent metal keep-outs on the PCB in the figure above.* • • • • • • • • • WFM200 PCB portion size is X = 17.5 mm and Y= 45 mm of metal. PCB may be slightly larger to account for PCB edge routing. Main portion of PCB X dimension can be any length.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3.5 WFM200 Portion One Corner Bias with 3 mm Metal Keep-Outs Figure 7.8. Reference Design for Extended X- and Y-dimensioned PCB Sizes with WFM200 Portion in Corner* Note: Spaces filled in black represent metal keep-outs on the PCB in the figure above.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.3.6 Recommended Antenna Loop Trace Capacitor Values This sections provides guidelines for antenna matching component values for various board sizes. System integrators should verify the antenna impedance in their full application with all housings and connections attached and mounted. The antenna matching component values can be adjusted to achieve Max VSWR of 2:1 in the actual application.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations 7.4 WFM200 Reference Evaluation Board Figure 7.9. WFM200 Evaluation Board Design with Expansion Header The carrier board size is 84 mm x 55 mm. The WFM200 section has a metallization of 17.5 mm x 55 mm. Figure 7.10.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations Figure 7.11. 2D Radiation Pattern of WFM200 Evaluation Board – Top View Figure 7.12. 2D Radiation Pattern of WFM200 Evaluation Board – Side View silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Layout Recommendations Figure 7.13. 2D Radiation Pattern of WFM200 Evaluation Board – Rear View Note: The X and Y axis are in the PCB plane cut as shown in the previous section, while the Z axis is orthogonal to the PCB. The typical antenna gain is +3.0 dBi and the antenna efficiency is -1 dB (= ~80%). silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Recommendations for Certification 8. Recommendations for Certification This section provides additional information on the certification details already provided in the WFM200 data sheet. WFM200 embeds TX power backoffs for 2:1 VSWR on its RF ports and is certified with an external connectorized coaxial dipole antenna and an integrated module antenna.
UG395: WFM200 Hardware Design User's Guide Recommendations for Certification 8.2 Certified Module Antenna The WFM200 SiP module has also been certified and designed to operate with the integrated module antenna. When using the module antenna, customer designs should ensure that the layout recommendations are carefully being followed as described in the previous sections in this document. The maximum module antenna gain with an appropriate carrier board size and proper layout design is +4.
UG395: WFM200 Hardware Design User's Guide Recommendations for Certification 8.3 CE Certification Requirements The Certification in CE Regions requires lower TX Power for the 1 Mbps and 2 Mbps 802.11b modulations. The amount of power reduction is based on the actual Max Gain specification of the Antenna used in the application. When the antenna gain reduces by 0.25 dB, the application may use 0.25 dB higher power settings for these two modulations. Use the PDS file for this purpose.
UG395: WFM200 Hardware Design User's Guide Package Outline 9. Package Outline BOTTOM VIEW silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Package Outline Table 9.1. Top Marking Description Dimension MIN NOM MAX A 1.20 1.30 1.40 A1 0.26 0.30 0.34 A2 0.95 1.00 1.05 b 0.27 0.32 0.37 D 6.50 BSC e 0.50 BSC E 6.50 BSC L 0.43 0.48 0.53 L1 0.11 0.16 0.21 L2 0.34 0.39 0.44 L3 0.24 0.29 0.34 L4 0.14 0.19 0.24 L5 0.62 0.67 0.72 aaa 0.10 bbb 0.10 ccc 0.10 ddd 0.10 eee 0.10 silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Package Outline Dimension MIN NOM MAX Note: 1. All dimensions in millimeters (mms). 2. Unless otherwise specified tolerances are: a. Decimal: • X.X = ±0.1 • X.XX = ±0.05 • X.XXX = ±0.03 b. Angular: ±0.1 (In Deg) 3. Hatching lines means package shielding area. 4. Dimensioning and Tolerance per ANSI Y14.5M-1994. silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Integral Antenna Loop and Keep-Out Required Dimensions 10. Integral Antenna Loop and Keep-Out Required Dimensions Figure 10.1. Integral Antenna Loop and Keep-Out Required Dimensions silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Integral Antenna Loop and Keep-Out Required Dimensions Figure 10.2. Dimensions and Coordinates for Integral Antenna Loop and Keep-Out Areas of WFM200 silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Recommended PCB Land Pattern 11. Recommended PCB Land Pattern Table 11.1. PCB Land Pattern Dimensions Dim mm b 0.32 D1 5.50 D2 4.77 D3 3.70 D4 2.63 D5 1.65 D6 4.00 D7 0.05 eD1 1.00 eD2 0.60 eD3 0.15 e 0.50 E1 5.70 E2 5.10 E3 2.92 E4 2.85 silabs.com | Building a more connected world. Preliminary Rev. 0.
UG395: WFM200 Hardware Design User's Guide Recommended PCB Land Pattern Dim mm E5 1.65 E6 4.50 E7 2.40 E8 1.20 E9 4.50 L 0.48 L1 0.67 eE1 0.60 eE2 0.60 Note: 1. All feature sizes shown are at Maximum Material Condition (MMC) and a card fabrication tolerance of 0.05 mm is assumed. 2. Dimensioning and Tolerance is per the ANSI Y14.5M-1994 specification. Table 11.2. Stencil Design Pad No. Pad Size (mm) Pad Coordinates (X, Y) 47 0.32 x 0.48 Pad Center Origin (0,0) 1 0.32 x 0.48 (0.
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