Analog Devices Inc. 101675-HMC544

Overview

HMC544 from Analog Devices (formerly Hittite Microwave) is a GaAs MMIC T/R SPDT switch for DC–4 GHz RF front-end signal routing in cellular infrastructure and wireless radios. It delivers 0.2 dB insertion loss at 1.0 GHz, +39 dBm input P1dB, and +55 dBm IP3 under +3 V control, operating with positive 0/+3 V or 0/+5 V logic to route RF signals between RFC and either RF1 or RF2 in base station transceivers.

For engineers reviewing the HMC544 datasheet, HMC544 pinout, HMC544 application, or HMC544 equivalent, this page provides verified package mapping (SOT26), functional truth table, RF port isolation vs. frequency, thermal derating data, and real-world linearity performance across temperature and control voltage.

Technical Context

The HMC544 implements a reflective GaAs PHEMT SPDT architecture where RF1 and RF2 present open-circuit terminations when off, minimizing load mismatch during switching. Its on-chip bias network enables low-current positive control (≤2 µA at +5 V) without external level-shifting circuitry.

Designed for medium-power T/R paths, it supports hot-switching up to +39 dBm with full DC–4 GHz bandwidth, validated across –40°C to +85°C operating range and MSL1 reflow compatibility. All RF ports require external DC blocking capacitors to maintain DC isolation and define low-frequency cutoff.

Key Specifications

Pinout & Package

Package: SOT26 (6-lead surface-mount plastic package, MSL1, Sn/Pb lead finish for HMC544; RoHS-compliant matte Sn for HMC544E). Dimensions per outline drawing: 2.9 mm × 1.6 mm × 1.1 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SPDT T/R switch applications.

Compared with HMC544E and QM11036, the HMC544 offers the highest input P1dB (+39 dBm) in its class and full symmetry across all three RF ports - critical for bidirectional TDD systems where RFC must serve as both input and output node with matched loss and isolation.

Availability

HMC544 is available at Aetrix Electronics and suitable for cellular infrastructure, microwave radio, and WLAN access point designs requiring stable component supply, consistent RF performance across temperature, and long-term obsolescence management.

Supply support for HMC544 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 Hittite Microwave in 2014 and integrates its high-frequency RF portfolio into ADI's broader signal chain solutions for communications, defense, and instrumentation.

The HMC544 belongs to Hittite's legacy GaAs MMIC SPDT switch product line, engineered specifically for high-linearity, medium-power T/R switching in 450 MHz–4 GHz wireless infrastructure equipment.

FAQ

What is the maximum RF input power the HMC544 can handle without damage?

The HMC544 has an absolute maximum RF input power rating of +39 dBm under 0/+5 V control conditions. This applies to continuous wave (CW) signals and accounts for hot-switching capability. Exceeding this level risks permanent degradation of the GaAs PHEMT devices. Derating is required above +85 °C ambient per the 7.14 mW/°C thermal specification. The HMC544 datasheet specifies +39 dBm as both the hot-switch power level and maximum RF input power limit.

Does the HMC544 require external DC blocking capacitors, and why?

Yes, the HMC544 requires external DC blocking capacitors at all three RF ports (RFC, RF1, RF2) because its internal RF path is DC-coupled and matched to 50 Ω. Without these capacitors, DC bias from preceding or following stages would disrupt the HMC544's internal bias network and potentially damage connected components. Capacitor value determines the low-frequency cutoff - for example, a 330 pF capacitor sets f_3dB ≈ 10 MHz. The HMC544 evaluation board (101675) uses 330 pF 0402 capacitors.

How does the HMC544 behave when powered down or with floating control inputs?

The HMC544 does not have a defined power-down state - it operates from DC control voltages only and lacks an enable/disable pin. With floating A and B inputs, the internal bias network may pull them to indeterminate logic levels, resulting in unpredictable RF path selection or degraded isolation. The datasheet mandates driving A and B with valid 0/+3 V or 0/+5 V logic; unused control lines must be terminated to GND or Vdd. The HMC544 truth table defines only low/high states - no high-impedance mode exists.

Can the HMC544 replace the HMC544E in an existing design?

Yes, the HMC544 can replace the HMC544E in most cases because both share identical electrical specifications, pinout, and SOT26 footprint. The primary difference is lead finish: HMC544 uses Sn/Pb (235 °C max reflow), while HMC544E uses RoHS-compliant matte Sn (260 °C max reflow). If the PCB assembly process uses lead-free reflow, HMC544E is required; otherwise, HMC544 is functionally interchangeable. No layout changes are needed for the HMC544 replacement.

What is the thermal resistance and power dissipation limit of the HMC544?

The HMC544 has a junction-to-case thermal resistance of 140 °C/W and a maximum continuous power dissipation of 0.465 W at +85 °C case temperature. Above +85 °C, power must be linearly derated at 7.14 mW/°C - for example, at +105 °C case temperature, max dissipation drops to 0.322 W. This thermal profile assumes all ground leads (pins 2, 4, 6) are soldered to a low-impedance RF ground plane, as specified in the HMC544 package notes.