Analog Devices Inc. HMC939LP4

Overview

HMC939LP4 from Analog Devices (formerly Hittite Microwave) is a GaAs MMIC 5-bit digital attenuator IC for RF signal conditioning in microwave and millimeter-wave systems. It delivers 1.0 dB LSB steps across 0.1–33 GHz, ≤5.5 dB typical insertion loss (0.1–18 GHz), ±0.4 dB typical step error, and +43 dBm input IP3 at 0.5–33 GHz - enabling precise amplitude control in high-frequency test equipment and radar front-ends.

For engineers reviewing the HMC939LP4 datasheet, HMC939LP4 pinout, HMC939LP4 application, or HMC939LP4 equivalent, this part supports broadband RF design requiring stable attenuation accuracy, low bit error, high linearity, and surface-mount compatibility in space-constrained 16 mm² leadless packages.

Technical Context

The HMC939LP4 implements a monolithic GaAs-based switched-resistor architecture with five independent CMOS-compatible control inputs (P0–P4), each toggling between 0 V and +5 V to select discrete 1/2/4/8/16 dB attenuation bits. Its DC-coupled 50 Ω RF ports (RF1, RF2) require external blocking capacitors when DC bias is present.

Operating from dual supplies (Vdd = +5 V, Vss = −5 V), it draws only 2.5–6.5 mA Idd and −7.0 to −3.0 mA Iss, with 60 ns typical RF rise/fall time and 90 ns switching delay. Thermal resistance is 144 °C/W, supporting operation from −40 °C to +85 °C with MSL1 handling.

Key Specifications

Pinout & Package

16 mm² leadless plastic QFN package (HMC939LP4) with exposed thermal paddle; Sn/Pb lead finish, MSL1 rating, max reflow 235 °C. All ground leads and paddle must be soldered to PCB RF ground per Hittite land pattern guidelines.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar digital RF attenuator applications.

Compared with HMC1056LP4E and QM11036, the HMC939LP4 offers optimal balance of broadband linearity (+43 dBm IP3), tight step accuracy (±0.4 dB), and proven reliability in space-qualified and military platforms - making it preferred where Ka-band fidelity and low bit error are critical.

Availability

HMC939LP4 is available at Aetrix Electronics and suitable for fiber optic transceivers, microwave radio systems, and radar front-ends requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for HMC939LP4 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 precision signal chain solutions for defense, aerospace, and communications.

The HMC939LP4 belongs to Analog Devices' GaAs MMIC digital attenuator product line, engineered for broadband RF amplitude control in mission-critical microwave systems demanding low distortion and high repeatability.

FAQ

What is the operating frequency range of the HMC939LP4?

The HMC939LP4 operates from 0.1 GHz to 33.0 GHz, covering L-, S-, C-, X-, Ku-, K-, and lower Ka-bands. Its insertion loss remains ≤5.5 dB typical up to 18 GHz and ≤7.0 dB up to 26.5 GHz, making it suitable for wideband test instrumentation and satellite communication systems where consistent performance across decades of frequency is essential. The HMC939LP4 maintains specified return loss (>12 dB) and step accuracy across this entire band.

Does the HMC939LP4 require dual-supply biasing?

Yes, the HMC939LP4 requires dual supplies: Vdd = +5 V and Vss = −5 V. These rails power the internal GaAs FET switches and define the RF port DC operating point. Current draw is 2.5–6.5 mA on Vdd and −7.0 to −3.0 mA on Vss. Control inputs P0–P4 operate at 0 V / +5 V logic levels, independent of Vss. The HMC939LP4 will not function correctly with single-supply configurations.

What is the meaning of "LSB" in the HMC939LP4 specification?

In the HMC939LP4, "LSB" stands for Least Significant Bit and refers to the smallest discrete attenuation increment: 1.0 dB. With five bits (P0–P4) weighted 1/2/4/8/16 dB, the HMC939LP4 achieves 31 dB total range in exact integer steps. This 1.0 dB LSB enables deterministic amplitude control without interpolation - critical for automated calibration routines and standards-compliant RF testing where step repeatability directly impacts measurement uncertainty. The HMC939LP4 guarantees ±0.4 dB typical step error relative to insertion loss.

Can the HMC939LP4 be used in space applications?

Yes, the HMC939LP4 is qualified for space applications per its use case listing and heritage in radiation-tolerant designs. It operates from −40 °C to +85 °C, features Class 1A HBM ESD protection, and has been deployed in flight hardware for low-Earth orbit payloads. Its GaAs MMIC construction provides inherent resilience to total ionizing dose (TID), and the 16 mm² leadless package supports robust thermal management in vacuum environments. The HMC939LP4 data sheet explicitly cites "Space Applications" among its target uses.

How does the HMC939LP4 handle RF port DC coupling?

The HMC939LP4 RF1 and RF2 ports are DC-coupled and internally matched to 50 Ω, but require external DC blocking capacitors if the connected RF line carries non-zero DC potential. This prevents bias disruption and ensures proper large-signal operation. The HMC939LP4's pinout documentation confirms that no internal blocking is provided - users must place appropriate high-frequency capacitors (e.g., 1000 pF 0402) in series with each RF path. Failure to do so may cause shift in operating point or damage under mismatched DC conditions.