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40MHz to 3.8GHz Log RF Power Detector Features 75dB Dynamic Range

A new monolithic broadband, high performance logarithmic RF power detector from Linear Technology provides accurate RF power measurement over a wide frequency range covering the 800-900MHz and the 1.7GHz to 2.2GHz cellular bands, as well as the 2.6GHz and 3.5GHz WiMAX bands.

The LT5538 RF power detector provides a DC output voltage that is log-linearly proportional to its input power level. Within its measurement dynamic range, the detector exhibits best-in-class accuracy and linearity of +/- 0.8dB over its rated operating temperature range of -40°C to +85°C. Moreover, the LT5538 has outstanding sensitivity, capable of detecting signals as small as -75dBm to as large as +10dBm at 2.14GHz. The device operates with a single-ended RF input. It requires no external RF transformer, thus simplifying design while reducing costs.

The LT5538's dynamic range performance is ideal for RF power amplifier power control and monitoring for a wide range of wireless systems, as well as receiver AGC (Automatic Gain Control), and RSSI (Receive Signal Strength Indicator) functions. These are required functions for cellular basestations of all types, including large cells, microcells, picocells, and femtocells, wireless repeaters, WiMAX basestations, broadband wireless access points, broadband cable networks, military and commercial long-range radios, as well as test and measurement instrumentation. The LT5538’s accuracy performance helps to minimize equipment calibration requirements, resulting in stable system performance and reduced operating costs.

The LT5538 utilizes Linear Technology's high speed bipolar process, enabling wide bandwidth and dynamic range performance. The fast output response of 100ns rise time and 200ns fall time to rapidly changing RF input signal levels make it suitable for rapid measurement of RF signal power in TDD (Time Division Duplexing) switching wireless operating environments, including WiMAX, TD-SCDMA, and other applications.

The LT5538 operates over a wide supply voltage range of 3V to 5.25V, drawing a low quiescent supply current of 29mA compared to other similar class detectors. A shutdown feature is provided. When the chip is disabled with a logic LOW applied to its ENABLE input pin, the chip draws a typical shutdown current of 1uA, and a maximum of 100uA.

 3.8GHz High Dynamic Range RF Detector


Summary of Features: LT5538
Operating Frequency Range 40MHz to 3.8GHz
Accurate over Temperature
(-40°C to +85°C)
Log-Linear Dynamic Range  
       •@ 880MHz 75dB
       •@ 2.14GHz 70dB
Fast Response Time  
       •Rise Time 100ns
       •Fall Time                 200ns
Single-Ended Operation No External Transformer
Small Package 3mm x 3mm DFN


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