STM32W108C8U64TR STMicroelectronics

AN3206 Application note PCB design guidelines for the STM32W108 platform 1 Introduction STMicroelectronics provides a IEEE 802.15.4 product design engineer with a number of paths towards the successful design of a IEEE 802.15.4-compliant solution based on the STMicroelectronics STM32W108 family of system-on-chip (SoC) platforms. The STM32W108xx kits contain software, hardware, and documentation designed for developers to create applications efficiently on a tested and controlled platform. Once the design team is familiar with ST s STM32W108xx products and the available IEEE 802.15.4 software libraries and stacks, the next step in the design path involves designing application- specific hardware to meet product requirements. This application note is intended to accompany the reference designs and provide detailed information regarding the design decisions employed within STMicroelectronics designs. In addition, it details the design guidelines for developing an application-specific IEEE 802.15.4 design using an STM32W108xx device. After reading this document, developers should be able to successfully implement a design with an STM32W108xx device. For further information, visit the STMicroelectronics web site at www.st.com/stm32w. Due to the application-specific nature of STMicroelectronics reference designs, ST recommends that hardware designers familiarize themselves with the most recent reference design available. This document is applicable to the following STM32W108xx kits: STM32W108xx starter kit (part number: STM32W-SK) STM32W108xx extension kit (part number: STM32W-EXT) STM32W108xx low-cost RF control kit (part number: STM32W-RFCKIT) Note: The STM32W108 Reference Design is built on a 4-layer, FR-4 epoxy PCB. The STM32W108-based Reference Design includes the following elements: Schematics (in PDF format) Bill of materials (BOM) Gerber files While the Reference Design includes most of the information required to start an application-specific design, if additional items needed, please contact STMicroelectronics Customer Support on the STMicroelectronics web site www.st.com/stm32w. March 2011 Doc ID 17406 Rev 3 1/14 www.st.comContents AN3206 Contents 1 Introduction 1 2 Reference design . 3 2.1 RF design guidelines . 4 2.1.1 STM32W108 RF ports . 4 2.1.2 Optimizing for TX (Boost mode) 4 2.1.3 Matching network circuit design 5 2.1.4 Harmonic filter design . 8 2.1.5 Band-pass filter 8 2.1.6 Antenna matching circuit . 8 2.2 RF layout guidelines 9 2.2.1 PCB tolerance . 9 2.3 Other design considerations 9 3 Non-RF design considerations . 10 3.1 High-frequency (24-MHz) crystal reference (X1, C5, and C6) . 10 3.2 Optional Low-frequency crystal reference (X2, C27 and C26) . 11 3.3 1.8V regulator load capacitor 12 3.4 1.2V regulator loading . 12 3.5 1.8V net decoupling . 12 3.6 1.8V analog to 1.8V digital filtering 12 3.7 RF test connector . 13 4 Revision history . 13 2/14 Doc ID 17406 Rev 3