NXP Semiconductors AFT18HW355SR5

Overview

AFT18HW355SR5 from NXP Semiconductors (formerly Freescale) is an asymmetrical Doherty RF power LDMOS transistor designed for cellular base station amplifiers operating in the 1805–1880 MHz band. It delivers 63 W average RF output power at 28 V, achieves 48.9% drain efficiency at 1840 MHz, and supports single-carrier W-CDMA with 9.9 dB PAR input signal under 0.01% CCDF probability.

For engineers reviewing the AFT18HW355SR5 datasheet, AFT18HW355SR5 pinout, AFT18HW355SR5 application, or AFT18HW355SR5 equivalent, key selection criteria include its dual-gate architecture (Carrier/Peaking), integrated Doherty matching, thermal resistance of 0.47 °C/W (junction-to-case), ESD rating per HBM Class 2, and compatibility with digital predistortion systems for wide instantaneous bandwidth LTE and W-CDMA infrastructure.

Technical Context

This device implements a monolithic dual-LDMOS structure with separate gate terminals (RFinA/VGSA and RFinB/VGSB) and drain terminals (RFoutA/VDSA and RFoutB/VDSB), enabling independent biasing of carrier and peaking paths. Its internal input/output matching supports 50 Ω system integration without external broadband matching networks.

The asymmetrical Doherty topology operates with VDDA and VDDB tied to a common 28 V supply, IDQA = 1100 mA quiescent current on the carrier side, and VGSB = 1.45 Vdc on the peaking side. Load-pull data confirms optimal P1dB tuning at Zload ≈ 1.24 – j4.24 Ω (1840 MHz) for carrier operation and Zload ≈ 1.37 – j4.53 Ω for peaking operation.

Key Specifications

Pinout & Package

Package: NI-1230S-4, thermally enhanced ceramic/metal flange-mount package with 4-terminal configuration and isolated case (electrically floating).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar RF power amplifier applications.

Compared with AFM38035N and PD57018-E, the AFT18HW355SR5 provides frequency-specific optimization for Band 3, eliminates external matching components, and delivers best-in-class efficiency at 63 W-making it the preferred choice for cost-sensitive, high-volume LTE macrocell deployments where thermal envelope and layout simplicity are critical.

Availability

AFT18HW355SR5 is available at Aetrix Electronics and suitable for macrocell base stations, remote radio heads, and W-CDMA infrastructure upgrade modules requiring stable component supply, long-lifecycle support, and traceable sourcing for telecom OEMs.

Supply support for AFT18HW355SR5 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

NXP Semiconductors acquired Freescale's RF Power business in 2015 and continues to develop high-efficiency LDMOS transistors for cellular infrastructure, broadcast, and industrial RF heating.

The AFT18HW355SR5 belongs to NXP's Airfast family of asymmetrical Doherty transistors, engineered specifically for energy-efficient, digitally predistorted macrocell and massive MIMO base station power amplifiers.

FAQ

What is the recommended gate bias voltage for the peaking path of AFT18HW355SR5?

The AFT18HW355SR5 peaking path (Pin 4, RFinB/VGSB) is specified for VGSB = 1.45 Vdc under typical W-CDMA functional test conditions (IDQA = 1100 mA, Pout = 63 W avg.). This bias point enables optimal Doherty efficiency enhancement while maintaining stable Class C operation. The device supports gate voltages from –6.0 V to +10 V, but deviation from 1.45 Vdc requires recalibration of DPD coefficients and load-pull verification.

Can AFT18HW355SR5 operate at 32 V drain supply as indicated in the Maximum Ratings table?

Yes, the AFT18HW355SR5 has a maximum VDD rating of +32 Vdc, but continuous operation above 28 V is not recommended for standard W-CDMA or LTE applications. At 32 V, the device exceeds its rated CW dissipation limit (259 W at 25 °C, derated to 0.64 W/°C), risking accelerated electromigration and reduced MTTF. Use 32 V only for pulsed or short-duration testing with strict thermal monitoring.

Does AFT18HW355SR5 require external input/output matching networks?

No, the AFT18HW355SR5 is internally matched for 50 Ω operation across 1805–1880 MHz, as confirmed in Freescale's functional test fixture documentation. External matching is unnecessary for baseline operation, though narrowband harmonic filters or isolators may be added for system-level stability or spectral purity. The NI-1230S-4 package integrates matching capacitors directly into the die substrate.

What is the thermal resistance junction-to-case (RθJC) value for AFT18HW355SR5, and how is it measured?

The AFT18HW355SR5 has RθJC = 0.47 °C/W, measured under CW conditions at TC = 77 °C, 63 W output, 28 Vdc, IDQA = 1100 mA, and VGSB = 1.45 Vdc at 1840 MHz. This value is derived per AN1955 methodology using calibrated thermocouples on the flange surface and infrared junction temperature estimation. It reflects worst-case thermal path from channel to mounting surface under full-rated load.

Is AFT18HW355SR5 compatible with digital predistortion (DPD) systems?

Yes, the AFT18HW355SR5 is explicitly designed for DPD-enabled systems, as stated in its features and verified by low AM/PM distortion (<22°) and stable ACPR (–29.2 dBc) across the 1805–1880 MHz band. Its asymmetrical Doherty architecture provides predictable memoryless nonlinearity, enabling fast DPD coefficient convergence in FPGA- or ASIC-based baseband processors used in commercial LTE eNodeBs.