Microwave Engineering Europe - November 2008 - (Page 31) RF SWITCHES 31 impact on the total solution cost. Figure 3 demonstrates how migration from wirebonding to flip-chip reduced the LTCC substrate area consumed by 43 percent, even when the switch increased from SP7T to SP9T. Ease of design Using a flip-chip IC requires less attention to control line routing and simplifies the printed circuit board (PCB) design. In addition, UltraCMOS devices do not require external bypassing or filtering components, so they simplify system layout. With flip-chip technology, the switch can be placed as a surface-mount device (SMD). Since all of the other components in the FEM are typically SMDs, the need for any wirebonding equipment is eliminated. Shipped in tape-and-reel form, flip-chip switches can be inserted into the FEM using standard placement machines. As an added advantage, mounted flip chips are less than 250 µm high, which reduces the overall module thickness—a critical concern to meet the height demands of super-slim handsets. UltraCMOS die includes shunting FETs on all ports, which significantly eases module design. It also improves performance because all signal paths are shunted to ground by the shunt FET, so noise generated in the rest of the system has no impact on the active path. ESD protection Shunt FETs also provide very high isolation performance, which relaxes the spurious requirements on transceivers and ensures protection of receive SAW filters from high RF power and ESD events. Because it is a CMOS technology, UltraCMOS can integrate ESD protection devices. Typical devices manufactured using this process have Class 2 (2000 V) HBM tolerance on control pins and 1500 V HBM tolerance on RF pins, so UltraCMOS switches are highly robust against ESD damage. This offers a few advantages. For instance, it reduces module fallout during manufacturing, and it dramatically reduces the ESD circuitry at the antenna required to meet the stringent worldwide ESD standard, IEC61000-4-2. As multimedia portable handsets continue to increase in complexity, the supporting switches will necessarily need to scale to higher throw counts. Fortunately, UltraCMOS RF switches are already being produced in high volume and provide competitive advantages to handset designers, especially in applications where very high IP3 is required. The future of switching will probably include multiple switches on a single die. These types of developments will fully exploit the advantages of UltraCMOS, but they are increasingly difficult for GaAs switches to achieve. Offering advantages in linearity, voltage handling, footprint, ease of design, and ESD tolerance, UltraCMOS is well positioned to handle the future needs of handset designers. References [1] Prjadeha, Irina and Rainer Koller, “Designing a single-chip, six-band UMTS transceiver for world-wide wireless connectivity.” http://www. mobilehandsetdesignline.com/ howto/197005074. WIRELESS SYSTEMS 802.11, Bluetooth®, ZigBee®, Proprietary, Data Modems RF Technologies for OEMs Reliable wireless—FAST. Data delivery can be critical in industry and commerce. Laird Technologies has the solution: a complete line of RF transceivers that are as reliable as cable, ready-to-embed, and agency-certified around the globe. global solutions: local supportTM www.lairdtech.com/wireles s Microwave Engineering ● November 2008 ● www.mwee.com http://www.mobilehandsetdesignline.com/howto/197005074 http://www.mobilehandsetdesignline.com/howto/197005074 http://www.lairdtech.com/wireless http://www.lairdtech.com/wireless http://www.mwee.com
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