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Down-converting mixer extends receiver bandwidth to 3.8GHz

Posted: 09 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:WiMAX? 3G? mixers? Linear Tech? GSM?

Linear Tech's LT5557 mixer

Linear Technology's LT5557, a 3.3V high-linearity, down-converting active RF mixer, elevates receiver dynamic range performance while extending bandwidth capability to cover 3G and WiMAX base station frequencies to 3.8GHz. The chips offers 24.7dBm IIP3, noise figure of 11.7dB and 2.9dB of gain at 1.95GHz. Its performance remains robust at WiMAX frequencies with 23.5dBm IIP3, and 1.7dB of gain at 3.6GHz.

Best-in-class LO isolation
This performance is achieved with a low -3dBm LO input drive level, enabling best-in-class LO isolation performance. Typical LO-to-RF isolation is better than 42dBc at 1.95GHz. The LT5557's power consumption is low for this class of high linearity mixers, typically 270mW from a 3.3V supply. The device incorporates on-chip RF transformers to enable convenient single-ended, 50 ohms matching at the RF and LO inputs. The combination yields an overall cost-effective, compact, easy-to-use and high-performance receiver solution for wireless base stations of all types.

The LT5557 incorporates a double-balanced active mixer core topology with on-chip LO buffer. Differential drive is employed internally throughout the mixer to maximize linearity and RF isolation. Conversion from single-ended to differential is accomplished through on-chip RF balun transformers at the RF and LO inputs. The device's wide operating bandwidth covers the 850-965MHz GSM and US cellular bands, as well as 1.7GHz to 2.1GHz 3G wireless services. The LT5557 also supports WiMAX operating in the US at 2.6GHz and worldwide at up to 3.8GHz.

Power efficiency
The LT5557 operates from a single 3.3V supply, drawing a quiescent supply current of 81.6mA. A shutdown feature is provided. When the chip is disabled, it draws a maximum sleep current of 100?A.

The device comes in a 16-lead 4-by-4mm QFN surface mount package. It is pin-compatible with the company's other high-performance down-converting mixers. Pricing starts at $5.95 each in 1,000-piece quantities. The product is available immediately from stock.

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Related Datasheets
Part Number Description Category
? LT5557 400MHz to 3.8GHz 3.3V High Linearity Downconverting RF Mixer Electromechanical - Keyboards, Relays and Switches



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