Analog Devices Inc. LT5568EUF#TRPBF

Overview

LT5568EUF#TRPBF from Analog Devices (formerly Linear Technology) is a 700MHz–1050MHz direct-conversion I/Q modulator IC for cellular infrastructure transmitters. It delivers +22.9dBm OIP3 at 850MHz, –46dBc image rejection, –43dBm carrier leakage, –154dBm/Hz noise floor at 5MHz offset, and operates from 4.5V to 5.25V supply. It enables high-linearity RF upconversion in W-CDMA, CDMA2000, and LTE base station front-ends.

For engineers reviewing the LT5568EUF#TRPBF datasheet, LT5568EUF#TRPBF pinout, LT5568EUF#TRPBF application, or LT5568EUF#TRPBF equivalent, key selection criteria include I/Q gain/phase imbalance (<0.07dB / <0.45°), integrated LO quadrature generator, 16-lead 4mm × 4mm QFN package with exposed ground pad, and DC-coupled 50Ω baseband interface requiring 0.54V common-mode voltage.

Technical Context

The LT5568EUF#TRPBF integrates differential voltage-to-current converters for I/Q baseband inputs, double-balanced upconverting mixers, an on-chip RF balun for 50Ω single-ended output, and a precision LO quadrature phase generator with buffer. Its architecture supports both direct modulation and image-reject upconversion modes via externally applied 90°-shifted baseband signals.

LO input is single-ended, AC-coupled, and matched to ~50Ω; RF output is also single-ended and AC-coupled. Baseband inputs BBPI/BBMI/BBPQ/BBMQ are DC-coupled with internal 0.54V bias and 100Ω differential impedance. Enable (EN) pin provides fast 0.3μs turn-on and 1.4μs turn-off switching between active and 50μA sleep modes.

Key Specifications

Pinout & Package

LT5568EUF#TRPBF is housed in a 16-lead 4mm × 4mm plastic QFN package (UF) with exposed thermal pad (Pin 17) that must be soldered to PCB ground for RF performance and thermal management.

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 LT5568EUF#TRPBF offers superior image rejection (–46dBc vs ≤–40dBc) and lower noise floor (–154dBm/Hz) within its 700–1050MHz sweet spot, making it the preferred choice for high-efficiency, spectrally demanding cellular infrastructure transmitters where LO integration and baseband interface simplicity are critical.

Availability

LT5568EUF#TRPBF is available at Aetrix Electronics and suitable for cellular infrastructure transmitters, CDMA2000 base stations, and RFID reader front-ends requiring stable component supply, consistent RF performance across temperature, and long-term lifecycle availability.

Supply support for LT5568EUF#TRPBF 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 through the acquisition of Linear Technology in 2017.

The LT5568EUF#TRPBF belongs to ADI's high-linearity RF modulator product line, engineered specifically for wireless infrastructure applications demanding exceptional ACPR, image rejection, and noise performance in 700–1050MHz cellular bands.

FAQ

What is the recommended LO input power for optimal performance of the LT5568EUF#TRPBF?

The LT5568EUF#TRPBF achieves best linearity and noise performance at 0dBm LO input power. At –5dBm, image rejection improves slightly but noise floor degrades by 1.5dB at POUT = 4dBm; at +5dBm, LO feedthrough increases with no gain in OIP3 or conversion gain. The datasheet specifies –10dBm to +5dBm operational range, with 0dBm as the design center point for all key specifications including OIP3, IR, and NFloor.

How should the baseband inputs of the LT5568EUF#TRPBF be biased for minimum LO feedthrough?

The LT5568EUF#TRPBF baseband inputs BBPI, BBMI, BBPQ, and BBMQ require a precise 0.54V DC common-mode voltage for optimal LO feedthrough suppression. If driven by a DAC with adjustable common-mode output, set it to 0.27V - because the LT5568EUF#TRPBF's internal bias network forms a voltage divider, resulting in 0.54V at the V-I converter input. Deviation from this level increases carrier leakage beyond the specified –43dBm.

Does the LT5568EUF#TRPBF require external filtering on its RF output?

Yes - a series AC-coupling capacitor is mandatory in the RF output path of the LT5568EUF#TRPBF during 1dB compression measurements and recommended in production designs. This prevents conduction through the internal ESD diode to ground when RF output exceeds 3dBm, which would otherwise degrade linearity and cause measurement errors. Typical value is 100nF, placed immediately after Pin 11 (RF).

What is the function of the exposed pad (Pin 17) on the LT5568EUF#TRPBF package?

The exposed pad (Pin 17) on the LT5568EUF#TRPBF is electrically connected to ground and serves two critical functions: (1) thermal dissipation - with θJA = 37°C/W, it must be soldered to a large PCB ground plane to prevent junction temperature exceedance; (2) RF grounding - it forms part of the RF return path for the internal balun and mixers, and omission causes measurable degradation in S22, image rejection, and LO feedthrough.

Can the LT5568EUF#TRPBF be used as an image-reject upconverting mixer?

Yes - the LT5568EUF#TRPBF can be configured as an image-reject upconverting mixer by applying 90° phase-shifted signals to the I and Q baseband inputs. In this mode, it rejects the image frequency (fLO – fBB) while passing the desired sum frequency (fLO + fBB), achieving –46dBc image rejection at 850MHz without external calibration. This capability is explicitly documented in the datasheet and leverages the same internal quadrature LO generation and balanced mixer topology used in direct modulation mode.