National Semi Intros LMVxxx Family of Power Detectors
National Semiconductor Corp. (Santa Clara, CA) introduced its LMVxxx family of radio frequency (RF) power detectors for wireless applications that require high frequency and range such as mobile phone power controls and power amplifier modules, wireless local area networks, and global positioning system navigation modules. The family includes small RF logarithmic amp and mean-square detectors that meet the criteria.
The LMV225, LMV226 and LMV228 are log amp RF power detectors with multi-band frequency ranges from 450 MHz to 2 GHz. The devices operate with a single supply from 2.7 V 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. The LMV225 can be used with a 30 dB 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 suitable for GSM, EDGE, GPRS, and TDMA applications. The output voltage ranges from 0.2 V to 2 V, and can be scaled down to meet analog-to-digital converter input-range requirements.
The LMV225 and LMV228 RF power detectors work in cooperation with the LM320x Series of supervisory power amplifiers (SuPA), allowing an adaptive PA supply control. The power detectors are used to control/drive the SuPA to achieve better power efficiency and accurate transmit power control. The SuPA generates the required supply voltage of the power amplifier for a given output transmit power; this combination of SuPA plus power detector generates the real-time optimum power supply voltage for a given RF transmit power.
The LMV225 and LMV228 are priced at $0.41, and the LMV226 is priced at $0.53, both in 1,000-unit quantities. All three chips are offered in standard or lead-free, micro SMD packages. The LMV232 is available in a lead-free, eight-bump, micro SMD package that is priced at $0.69 in 1,000-unit quantities.
