Analog Devices Inc. LT5579IUH#PBF

Overview

LT5579IUH#PBF from Analog Devices (acquired Linear Technology) is a high-linearity, single-ended LO input / single-ended RF output upconverting mixer optimized for 1.5GHz–3.8GHz RF output frequencies. It delivers +27.3dBm OIP3 at 2.14GHz, –158dBm/Hz noise floor at –5dBm POUT, and 2.6dB conversion gain with only –1dBm LO drive on a single 3.3V supply - enabling compact, low-power W-CDMA/LTE basestation transmitter designs.

For engineers reviewing the LT5579IUH#PBF datasheet, LT5579IUH#PBF pinout, LT5579IUH#PBF application, or LT5579IUH#PBF equivalent, key selection criteria include its wide RF bandwidth (900–3900MHz), low LO leakage (–35dBm typical), differential IF input interface, and QFN24 package thermal performance - all critical for high-dynamic-range wireless infrastructure transmitters.

Technical Context

The LT5579IUH#PBF integrates a high-gain LO buffer driving a double-balanced active mixer core with internal baluns, enabling single-ended LO and RF ports while maintaining excellent LO-to-RF isolation (>73dB) and IF-to-LO isolation (>81dB). Its differential IF input (240MHz–1000MHz range) is internally biased to 570mV common-mode voltage and requires external 11Ω resistors for optimal 50mA-side biasing.

Operation relies on precise external matching networks: a 4:1 IF transformer (e.g., MABAES0061), series inductors (40nH), and frequency-tuned capacitors (e.g., 33pF/82pF) to achieve >15dB IF return loss and >10dB RF return loss across target bands. Thermal management mandates soldering of the exposed pad (Pin 25) to a low-impedance PCB ground plane with multiple vias.

Key Specifications

Pinout & Package

LT5579IUH#PBF uses a 24-lead, 5mm × 5mm plastic QFN package (UH) with exposed thermal pad (Pin 25). The package requires soldering of the exposed pad to PCB ground for both electrical integrity and thermal dissipation (θJC = 3°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADL5375-05ACPZ-R7 and HMC774ALC3B, the LT5579IUH#PBF uniquely delivers active conversion gain with minimal LO drive in a compact QFN, making it optimal for cost- and power-sensitive wireless infrastructure where simplicity and integration outweigh the need for I/Q capability or passive robustness.

Availability

LT5579IUH#PBF is available at Aetrix Electronics and suitable for W-CDMA basestations, LTE small cells, and WiMAX fixed wireless access equipment requiring stable component supply across multi-year production cycles.

Supply support for LT5579IUH#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 digital signal processing semiconductors, serving communications, industrial, automotive, and healthcare markets.

The LT5579IUH#PBF belongs to ADI's high-frequency mixer product line, engineered specifically for wireless infrastructure transmitters demanding high linearity, low noise, and simplified RF layout in 1.5–3.8GHz bands.

FAQ

What is the minimum LO drive level required for specified performance of the LT5579IUH#PBF?

The LT5579IUH#PBF is characterized at –1dBm LO drive, delivering 2.6dB conversion gain and +27.3dBm OIP3 at 2.14GHz. Performance remains functional down to –5dBm LO, but conversion gain drops ~1.5dB and OIP3 degrades ~3dB. For production designs, –1dBm ±1dB is the recommended LO drive window to meet datasheet specifications reliably.

Can the LT5579IUH#PBF operate outside the 1.5GHz–3.8GHz RF range cited in the datasheet?

Yes - the LT5579IUH#PBF can operate from 900MHz to 3900MHz per AC Electrical Characteristics, though performance degrades below 1500MHz due to reduced RF transformer inductance. At 1750MHz, gain is 1.8dB and OIP3 is 29dBm; at 900MHz, gain falls to ~–2dB and OIP3 drops to ~22dBm, requiring careful system-level validation.

How should the exposed thermal pad (Pin 25) of the LT5579IUH#PBF be connected on the PCB?

The exposed pad (Pin 25) of the LT5579IUH#PBF must be soldered directly to a solid, low-impedance RF ground plane on the top layer. At least four 0.3mm-diameter thermal vias should connect this pad to inner ground planes and the bottom-layer ground pour to achieve θJA ≤ 34°C/W. Failure to properly solder the pad risks junction temperature exceeding 150°C under full load.

What is the purpose of the 11Ω resistors on the IF+ and IF– pins of the LT5579IUH#PBF?

The 11Ω resistors on IF+ and IF– pins of the LT5579IUH#PBF set the DC bias current through the mixer core to ~50mA per side, optimizing linearity and noise figure. These resistors also establish the differential input impedance (~10Ω) and must be 0.1% tolerance to maintain symmetry and minimize LO leakage. Their placement must be symmetric and close to the IC pins.

Does the LT5579IUH#PBF require external matching components for the LO input?

External LO matching is not required above 1.1GHz, where the LT5579IUH#PBF achieves >9dB return loss (e.g., 11dB at 2300MHz). Below 1.1GHz, external components (e.g., series inductor + shunt capacitor) are necessary to improve match - Table 3 in the datasheet provides impedance data for designing such networks at 750MHz or 1000MHz LO frequencies.