Analog Devices Inc. DC2035A

Overview

LTC5551 from Analog Devices (formerly Linear Technology) is an ultra-high dynamic range, broadband active downconverting mixer IC optimized for RF receiver front-ends in cellular infrastructure and defense systems. It operates from 300MHz to 3.5GHz RF input, supports 200MHz–3.5GHz LO, delivers +35.5dBm typical IIP3 at 1950MHz, 2.4dB conversion gain, <10dB SSB noise figure, and 670mW power consumption at 3.3V. A key application is LTE-Advanced basestation receivers covering 700MHz–2.7GHz.

For engineers reviewing the LTC5551 datasheet, LTC5551 pinout, LTC5551 application, or LTC5551 equivalent, this page provides verified circuit role (active double-balanced downconverter), package mapping (16-lead 4mm × 4mm QFN), validated pin functions (e.g., EN for enable, ISEL for low-power mode), thermal sensing capability (TEMP diode), and two confirmed alternative mixers with documented performance trade-offs.

Technical Context

The LTC5551 integrates a double-balanced passive mixer core with on-die IF buffer amplifier and LO driver, enabling high linearity without external baluns. Its RF and LO inputs are single-ended 50Ω-matched; IF output is differential with open-collector outputs requiring external biasing via IFBIAS or transformer center-tap.

It supports both low-side and high-side LO injection, features integrated temperature sensing (TEMP pin), and offers dual power modes: normal mode (204mA @ 3.3V, +35.5dBm IIP3) and low-power mode (142mA @ 3.3V, +29.3dBm IIP3). Turn-on/turn-off time is 0.4µs/0.5µs, and operation spans –40°C to 105°C case temperature.

Key Specifications

Pinout & Package

Package: 16-lead (4mm × 4mm) plastic QFN with exposed pad (Pin 17), RoHS-compliant, –40°C to 105°C operating temperature range.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar downconverting mixer applications.

Compared with HMC1040LP4CE and MAX2035, the LTC5551 delivers superior third-order linearity (+35.5dBm IIP3) and integrated IF amplification-critical for high-fidelity signal capture in infrastructure-grade receivers-while maintaining industry-standard 4mm × 4mm QFN packaging and thermal sensing capability.

Availability

LTC5551 is available at Aetrix Electronics and suitable for LTE-Advanced basestations, DPD observation receivers, and avionics transponders requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for LTC5551 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 acquired Linear Technology in 2017 and maintains its high-performance RF product lines with rigorous qualification for industrial and aerospace applications.

The LTC5551 belongs to Linear's precision RF mixer family, designed specifically for demanding wireless infrastructure receivers where dynamic range, noise performance, and thermal stability are non-negotiable.

FAQ

What is the recommended LO drive level for optimal performance of the LTC5551?

The LTC5551 is specified for 0dBm LO drive (±6dB range). At 0dBm, it achieves +35.5dBm IIP3 and 2.4dB conversion gain at 1950MHz. Driving below –6dBm degrades conversion gain and increases noise figure; above +6dBm risks LO port damage and spurious generation. The LTC5551 datasheet confirms 0dBm as the nominal condition for all AC electrical characteristics.

Does the LTC5551 support both low-side and high-side LO injection?

Yes, the LTC5551 supports both low-side and high-side LO injection across its full 200MHz–3.5GHz LO range. Performance data in the datasheet shows IIP3, conversion gain, and noise figure across both configurations-for example, +35.5dBm IIP3 at 1950MHz RF with low-side LO and +35.2dBm with high-side LO. No hardware change is needed; only LO frequency selection differs.

How does the ISEL pin affect the performance of the LTC5551?

Pulling ISEL high activates low-power mode, reducing supply current by ~30% (from 204mA to 142mA at 3.3V) but trading off linearity: IIP3 drops from +35.5dBm to +29.3dBm at 1950MHz. Noise figure improves slightly (<9.2dB), and conversion gain remains stable at 2.4dB. This mode is ideal for standby or reduced-duty-cycle operation where power savings outweigh peak linearity needs.

What is the function of the TEMP pin on the LTC5551?

The TEMP pin connects to the anode of an on-die temperature-sensing diode. By forcing a known current (e.g., 10µA or 80µA) and measuring the forward voltage (726mV or 783mV at 25°C), designers can calculate die temperature using the specified voltage temperature coefficient (–1.72mV/°C). This enables real-time thermal monitoring and protection in high-power RF modules.

Can the LTC5551 be used with a 50Ω single-ended IF output configuration?

No-the LTC5551 IF outputs (IF+ and IF–) are differential open-collector nodes requiring external biasing and termination. A 50Ω single-ended IF interface is not supported natively. To interface with single-ended IF stages, designers must use a balun (e.g., Mini-Circuits TC4-1W-7ALN+) or active differential-to-single-ended amplifier. The datasheet specifies 950Ω||1.2pF differential load impedance at 153MHz.