Analog Devices Inc. 104769-HMC321LP4

Overview

HMC321LP4 from Analog Devices (formerly Hittite Microwave) is a GaAs MMIC SP8T non-reflective positive-control RF switch operating from DC to 8 GHz, delivering 2.5 dB typical insertion loss and >30 dB isolation at 6 GHz in 50-Ω systems, with integrated 3:8 TTL decoder for simplified logic control in broadband signal routing applications.

For engineers reviewing the HMC321LP4 datasheet, HMC321LP4 pinout, HMC321LP4 application, or HMC321LP4 equivalent, key selection considerations include its +5 V bias requirement, 0/+5 V positive TTL control interface, 4×4 mm leadless SMT package, DC–8 GHz bandwidth, and non-reflective architecture enabling stable impedance matching across all RF ports.

Technical Context

The HMC321LP4 implements a GaAs MESFET-based SP8T architecture with on-die binary decoder, reducing external control lines from eight to three (CTLA, CTLB, CTLC). Its non-reflective design maintains 50-Ω termination in both "on" and "off" states, minimizing system-level VSWR degradation during switching.

It requires DC blocking capacitors at RFC and all eight RF ports (RF1–RF8), with lowest usable frequency determined by capacitor value. Bias is fixed at +5 V ±10% (VDD), drawing 5 mA typical current, and operates over –40°C to +85°C.

Key Specifications

Pinout & Package

Package: 4×4 mm leadless surface-mount (QFN-style) with exposed ground paddle; RoHS-compliant variant HMC321LP4E uses matte Sn finish; MSL1 rating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SP8T RF switch applications.

Compared with HMC321LP4, HMC349ALP4E offers higher isolation but lacks DC coupling and SP8T capability, while QM11036 provides SP8T functionality without integrated decoding and reduced high-frequency coverage - making HMC321LP4 uniquely suited for DC–8 GHz, space-constrained, decoder-integrated designs.

Availability

HMC321LP4 is available at Aetrix Electronics and suitable for broadband test instrumentation, fiber-optic transceiver modules, switched filter bank systems, and sub-8 GHz wireless infrastructure requiring stable component supply and long-term obsolescence mitigation.

Supply support for HMC321LP4 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 IC portfolio into precision RF signal chain solutions for communications, defense, and instrumentation markets.

The HMC321LP4 belongs to Hittite's legacy GaAs MMIC SPnT switch product line, engineered for broadband, non-reflective RF path selection in DC–8 GHz systems where integration, low loss, and high isolation are critical.

FAQ

What is the minimum operating frequency of the HMC321LP4?

The HMC321LP4 operates from DC, but DC blocking capacitors are required at RFC and RF1–RF8 ports; the lowest usable frequency depends on capacitor value - for example, a 100 pF capacitor sets f_low ≈ 16 MHz. The device itself supports true DC coupling when capacitors are omitted, though system-level DC path requirements may dictate capacitor use.

Does the HMC321LP4 require negative voltage for control?

No, the HMC321LP4 uses exclusively positive control voltages: logic low is 0 to +0.8 V, logic high is +2.0 to +5.0 V, fully compatible with standard TTL and CMOS outputs. No negative supply or level-shifting circuitry is needed for interface with microcontrollers or FPGAs.

Can the HMC321LP4 be used in 75-Ohm systems?

Yes, the HMC321LP4 is specified for both 50-Ω and 75-Ω systems per its General Description. While optimized for 50-Ω impedance, its non-reflective architecture and matched ports allow direct use in 75-Ω video and CATV infrastructure with verified return loss and isolation performance.

What is the purpose of Pin 20 (N/C) on the HMC321LP4?

Pin 20 is designated N/C (no-connect) but must be connected to PCB RF ground to maximize off-state isolation. Leaving it floating degrades isolation by up to 10 dB due to parasitic coupling; grounding it completes the RF shield structure around the internal switch core.

Is thermal derating required for the HMC321LP4 at +85°C ambient?

No thermal derating is specified for the HMC321LP4 within its rated operating temperature range (–40°C to +85°C); all electrical specifications - including insertion loss, isolation, and IP3 - are guaranteed across this full range per the datasheet's TA = +25°C testing with characterization curves confirming stable performance up to +85°C.