RF power detectors suit high-frequency wireless apps - Embedded.com

RF power detectors suit high-frequency wireless apps

A family of RF power detectors is suited for wireless applications that require high frequency and range, such as mobile phone power controls and power amplifier modules, wireless LANs, GPS navigation modules. Linearity-in-dB, stability, reliability and accuracy are important criteria for RF applications. This family includes the smallest RF logarithmic amp and mean-square detectors that meet these criteria. These devices give RF designers the RF system performance, high reliability, ease of use, and flexibility to meet worldwide standards for communications certification, delivering a scalable technology for current and next- generation CDMA, WCDMA, and other 3G applications.

National Semiconductor's LMV225, LMV226, and LMV228 are log amp RF power detectors with multi-band frequency ranges from 450 MHz to 2 GHz. These devices provide an accurate temperature and supply-compensated output voltage that relates linearly to the RF input power in dBm. The devices operate with a single supply from 2.7 to 5.5 V.

The LMV225 has an RF power detection range from -30 dBm to 0 dBm and is suited for direct use in combination with resistive taps, eliminating the need for a directional coupler. If preferred, the LMV225 can also be used with a 30- to 35-dB directional coupler. The LMV226 and LMV228 have a detection range from -15 dBm to 15 dBm and are intended for use in combination with a 20-dB directional coupler. The LMV225 and LMV228 are targeted for the CDMA and WCDMA applications, while the LMV226 is equipped with a buffered output, which makes it suitable for GSM, EDGE, GPRS, and TDMA applications. These devices remain in a low-power-consumption shutdown mode until powered up through the enable pin to drive the power down. The output voltage ranges from 0.2 to 2 V and can be scaled down to meet analog-to-digital converter input range requirements.

The LMV225 and LMV228 are priced at $0.41, and the LMV226 sells for $0.53, all in 1000-unit quantities. More information on the LMV225 is available at www.national.com/pf/LM/LMV225.html; more information on the LMV226 is available at www.national.com/pf/LM/LMV226.html; and more information on the LMV228 is available at www.national.com/pf/LM/LMV228.html.

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