4031-T-B1 B 434

AN414 EZRADIOPRO LAYOUT DESIGN GUIDE 1. Introduction The purpose of this application note is to help users design EZRadioPRO PCBs using design practices that allow for good RF performance. This application note also help designers by separating TX and RX concerns. The RF performance and the critical maximum peak voltage on the output pin strongly depend on the PCB layout as well as the design of the matching networks. For optimal performance, Silicon Labs recommends the use of the PCB layout design hints described in the following sections. 2. Design Recommendations when Using EZRadioPRO RF ICs Extensive testing has been completed using reference designs provided by Silicon Labs. It is recommended to designers to use the reference designs as-is since they minimize detuning effects caused by parasitics, component placement, and PCB routing. When layouts cannot be followed as shown by the reference designs (due to PCB size and shape limitations), the following layout design rules are recommended. 2.1. Guidelines for Layout Design when Using the Si4430/31 The Si4430/31 devices use a Class-E type TX matching network with a typical output power level of +13 dBm at VDD = 3.3 V. Two basic types of board layout configurations exist at all frequency bands: the Split TX/RX type and the Direct Tie type. In the Split TX/RX type, the TX and RX paths are separated, and individual SMA connectors are provided for each path. In the Direct Tie type, the TX and RX paths are connected together directly, without any additional RF switch. The operating principle of both types and the reference designs with element values are given in AN436: Si4030/4031/4430/4431 PA Matching for wirewound and multilayer type 0402 size SMD inductances as well. The Split and Direct Tie type boards have slightly different PCB layouts, which are described in separate sections. 2.1.1. Split Type Matching Network Layout Based upon the 4431-T-B1 B Test Card (Separate TX and RX Paths with Two Antennas) Examples shown in this section of the guide are based upon the layout of the 4431-T-B1 B test cards. These cards contain two separate antennas for the TX and RX paths. This type of test card is best suited for demonstrating the output power and sensitivity of the EZRadioPRO RFICs. For this purpose, the TX and RX path layouts are separated and isolated as much as possible to minimize the mutual coupling effects. This type of test card is recommended for laboratory evaluation and not for range tests because the presence of two closely-spaced antennas may cause shadowing when receiving a radiated signal. The main layout design concepts are reviewed through this layout to demonstrate the basic principles. However, for an actual application, the layouts of the test cards with a single antenna (or with antenna diversity) should be used as references. The schematic of the Split type matching network for Si4431 RevB1 is shown in Figure 1. Rev. 0.2 12/10 Copyright 2010 by Silicon Laboratories AN414AN414 Figure 1. Schematic of the Split Type Matching Network for the Si4431 RevB1 The layout structure of the Split type matching network is shown in Figure 2. 2 Rev. 0.2