AD6432 Datasheet | Analog Devices

FEATURES Fully pliant with Standard and Enhanced GSM Specification DC-350 MHz RF Bandwidths 80 d B Gain Control Range I/Q Modulation and Demodulation Onboard Phase Locked Tunable Oscillator On-Chip Noise Roofing IF Filters Ultralow Power Design 2.7 V- 3.6 V Operating Voltage User-Selectable Power-Down Modes Small 44-Lead TQFP Package Interfaces Directly with AD20msp410 and AD20msp415 GSM Baseband Chipsets APPLICATIONS I/Q Modulated Digital Wireless Systems GSM Mobile Radios GSM PCMCIA Cards GSM 3 V Transceiver IF Subsystem AD6432 FUNCTIONAL BLOCK DIAGRAM IF SYNTH RF SYNTH OP AMP GENERAL DESCRIPTION The AD6432 IF IC provides the plete transmit and receive IF signal processing, including I/Q modulation and demodulation, necessary to implement a digital wireless transceiver such as a GSM handset. The AD6432 may also be used for other wireless TDMA standards using I/Q modulation. The AD6432’s receive signal path is based on the proven architecture of the AD607 and the AD6459. It consists of a mixer, gain-controlled amplifiers, integrated roofing filter and I/Q demodulators based on a PLL. The low noise, high-intercept variable-gain mixer is a doubly-balanced Gilbert-cell type. It has a nominal - 13 d Bm input-referred 1 d B pression point and a 0 d Bm input-referred third-order intercept. The gain-control input accepts an external control voltage input from an external AGC detector or a DAC. It provides an 80 d B gain range with 27.5 m V/d B gain scaling, where the mixer and the IF gains vary together. The I and Q demodulators provide inphase and quadrature baseband outputs to interface with Analog Devices’ AD7015 and AD6421 (GSM, DCS1800, PCS1900) baseband converters. An onboard quadrature VCO, externally phase-locked to the IF signal, drives the I and Q demodulators. The quadrature phase-locked oscillator (QPLO) requires no external ponents for frequency control or quadrature generation, and demodulates signals at standard GSM system IFs of 13...