RF ICs Complement Full Device Portfolio

Nov. 1, 2002
Low-cost RF ICs are now available from a long-time device supplier that is probably better known for its power-management circuits, operational amplifiers, and data converters.

Integrated-circuit (IC) suppliers are often known for a handful of circuit functions, such as microcontrollers or data converters. But Linear Technology Corp. (Milpitas, CA), already well-established for their power ICs, operational amplifiers, and digital-to-analog converters (DACs), is in the process of establishing themselves as a major supplier of RF ICs with the introduction of several new devices, including a high-linearity 3-GHz downconverting mixer, a 1-GHz RF power detector, and modulator/demodulator.

For example, the LT5512 is a high-linearity active downconversion mixer specified for input frequencies from DC to 3 GHz. The mixer offers input third-order intercept point (IP3) of +20 dBm at 950 MHz and +17 dBm at 1900 MHz. The IC includes a differential local-oscillator (LO) buffer amplifier (allowing it to work with single-ended and differential LO signals) and active double-balanced mixer. It provides typical conversion gain of 1 dB at 1900 MHz. The single-sideband (SSB) noise figure is 14 dB at 1900 MHz. The mixer, which is designed for supplies of +4.50 to +5.25 VDC, is supplied in a QFN package measuring just 4 × 4 mm.

The LTC5507 is an RF power-detector IC with input-frequency range of 100 kHz to 1 GHz and power-detection range of −34 to +14 dBm. The LTC5507 offers a modulation bandwidth of 1.5 MHz to handle such applications as envelope detectors, wireless data modems, amplitude-modulation (AM) and amplitude-shift-keying (ASK) demodulators, mobile telephones, and optical power detectors. The IC features an on-chip temperature-compensated Schottky-diode peak detector with extended dynamic range and output buffer to maintain power-detection accuracy over a temperature range of −40 to +85°C. It is designed to operate on supplies from +2.7 to +6.0 VDC with supply current of only 550 µA and low shutdown current of less than 2 µA.

The LT5503 in-phase/quadrature (I/Q) modulator/mixer also operates on supplies of +1.80 to +5.25 VDC. It is designed for input carrier frequencies from 1.2 to 2.7 GHz (at power levels from −20 to −10 dBm). It supports a 120-MHz I/Q input modulation bandwidth, and delivers modulated output signals of −3.0 dBm at 2.5 GHz. An on-board variable-gain amplifier provides output-power reduction in three steps (4.5, 9.0, and 13.5 dB) with 100-ns switching speed. Linear Technology Corp., 720 Sycamore Dr., Milpitas, CA 95035; (408) 432-1900, FAX: (408) 434-0507, Internet: www.linear.com.

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