Log RF Power Detector From Linear Technology

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.