Analog Devices Inc. LT5571EUF#PBF

Overview

LT5571EUF#PBF from Analog Devices (formerly Linear Technology) is a 620MHz–1100MHz direct quadrature I/Q modulator for wireless infrastructure transmitters. It delivers –4.2dB conversion gain, 21.7dBm OIP3 at 900MHz, –53dBc image rejection, –42dBm carrier leakage, and –159dBm/Hz noise floor at 20MHz offset. It serves as the RF upconversion stage in GSM, CDMA2000, and LTE base station transmit chains.

For engineers reviewing the LT5571EUF#PBF datasheet, LT5571EUF#PBF pinout, LT5571EUF#PBF application, or LT5571EUF#PBF equivalent, key selection criteria include I/Q gain/phase imbalance (<0.013dB / <0.24°), LO input power range (–10 to +5dBm), 16-lead 4mm × 4mm QFN package with exposed ground pad, and DC-coupled 0.5V common-mode baseband interface.

Technical Context

The LT5571EUF#PBF integrates dual voltage-to-current converters driving double-balanced mixers, an on-chip RF balun for 50Ω single-ended output, and a precision LO quadrature generator with integrated buffer. Its architecture enables direct baseband-to-RF conversion without external phase-shifting components.

It operates with 4.5V–5.25V supply, draws 97–120mA in active mode, and supports shutdown via EN pin (1V threshold). Baseband inputs (BBPI/BBMI/BBPQ/BBMQ) present 90kΩ differential impedance and require 0.5V DC bias; LO and RF ports are AC-coupled, 50Ω-matched, single-ended interfaces.

Key Specifications

Pinout & Package

The LT5571EUF#PBF is housed in a 16-lead 4mm × 4mm plastic QFN package with exposed ground pad (Pin 17), requiring soldering to PCB for thermal and RF grounding.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar direct-conversion modulator applications.

Compared with ADL5375-05ACPZ-R7 and TRF3705IRGZT, the LT5571EUF#PBF offers superior integrated quadrature generation and tighter factory-trimmed I/Q imbalance, making it optimal for fixed-frequency infrastructure where LO path simplicity and uncalibrated image rejection are critical.

Availability

LT5571EUF#PBF is available at Aetrix Electronics and suitable for cellular base station transmitters, CDMA2000 multi-carrier systems, and RFID interrogators requiring stable component supply and long-term industrial lifecycle support.

Supply support for LT5571EUF#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and RF ICs, formed by the acquisition of Linear Technology in 2017.

The LT5571EUF#PBF belongs to ADI's high-linearity RF modulator product line, designed specifically for wireless infrastructure applications demanding low distortion, high image rejection, and robust thermal performance in continuous transmit operation.

FAQ

What is the recommended common-mode voltage for LT5571EUF#PBF baseband inputs?

The LT5571EUF#PBF requires a 0.5V DC common-mode voltage on all four baseband inputs (BBPI, BBMI, BBPQ, BBMQ) to maximize dynamic range and minimize distortion. This voltage must be externally applied and held below 0.6V to prevent damage. Deviations from 0.5V degrade OIP3, OP1dB, and image rejection - for example, at 0.6V VCM, OIP3 drops from 21.7dBm to 22.1dBm but LO feedthrough worsens from –43.1dBm to –41.2dBm.

Does LT5571EUF#PBF require external LO phase-shifting circuitry?

No, the LT5571EUF#PBF integrates a precision LO quadrature phase generator and buffers, eliminating the need for external 90° hybrids or polyphase filters. This internal circuitry delivers accurate in-phase and quadrature LO signals to the I/Q mixers across 750–1100MHz, enabling >45dB uncalibrated image rejection. External phase shifters are unnecessary unless operating outside this range.

What is the absolute maximum rating for LT5571EUF#PBF supply voltage?

The absolute maximum supply voltage for LT5571EUF#PBF is 5.5V. Operation above 5.25V (maximum rated) risks parametric degradation and reduced reliability. The device is specified for 4.5V–5.25V operation, with supply current varying from 97mA to 120mA across this range at 25°C. Exceeding 5.5V may cause permanent damage per Absolute Maximum Ratings.

How does LT5571EUF#PBF handle RF output matching?

The LT5571EUF#PBF features an on-chip RF balun that transforms internal differential mixer outputs to a 50Ω single-ended RF output. Its S22 is 12.7dB at 900MHz with LO enabled; no external matching network is required for nominal operation. However, a series capacitor is recommended in the RF output line above +3dBm to prevent ESD diode conduction, which degrades linearity.

Can LT5571EUF#PBF be used as an image-reject upconverting mixer?

Yes, the LT5571EUF#PBF can be configured as an image-reject upconverting mixer by applying 90° phase-shifted signals to the I and Q inputs - for example, using two separate LO sources or a calibrated external splitter. In this mode, it leverages the same high linearity (21.7dBm OIP3) and low noise floor (–159dBm/Hz) while rejecting the image band by –53dBc at 900MHz without additional filtering.