Analog Devices Inc. HMC624LP4E

Overview

HMC624LP4E from Hittite Microwave Corporation is a GaAs MMIC 6-bit digital RF attenuator with 0.5 dB LSB resolution, DC–6 GHz bandwidth, 31.5 dB attenuation range, and integrated 3-wire SPI-compatible serial interface (SERIN/CLK/LE). It operates from single +3 V or +5 V supply and delivers low insertion loss (2.2 dB @ 3.5 GHz) in cellular infrastructure and microwave radio signal conditioning paths.

For engineers reviewing the HMC624LP4E datasheet, HMC624LP4E pinout, HMC624LP4E application, or HMC624LP4E equivalent, key selection criteria include its dual-mode control (serial/parallel), user-selectable power-up state, ±0.25 dB typical step error, high input IP3 (+55 dBm), and RoHS-compliant 4×4 mm QFN package requiring no external matching components.

Technical Context

The HMC624LP4E implements a broadband GaAs MMIC architecture with off-chip AC-ground capacitors enabling near-DC operation. Its dual-mode digital interface supports both 3-wire SPI (P/S = high) and 6-bit parallel (P/S = low) control, with latch-enable (LE) synchronization for stable state transitions.

It features a programmable power-up state determined by either D0–D5 logic levels or dedicated PUP1/PUP2 pins, and includes a serial output (SEROUT) for cascading with other Hittite serial devices. Biasing uses a single Vdd rail (3 V or 5 V), with CMOS/TTL-compatible digital inputs and 50 Ω matched RF ports (ATTIN/ATTOUT).

Key Specifications

Pinout & Package

The HMC624LP4E is housed in a RoHS-compliant 4×4 mm, 24-lead QFN package with exposed thermal paddle. All ground leads (pins 5, 14, 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 HMC1084LP4E and QM11030, the HMC624LP4E offers optimal balance of 6-bit resolution, DC–6 GHz coverage, +55 dBm linearity, and full serial/parallel flexibility - making it preferred for high-performance infrastructure and test instrumentation where configurability and signal fidelity are critical.

Availability

HMC624LP4E is available at Aetrix Electronics and suitable for cellular infrastructure, microwave radio, and RF test equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.

Supply support for HMC624LP4E 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

Hittite Microwave Corporation (now part of Analog Devices) specialized in high-frequency RFICs, MMICs, and microwave components for defense, communications, and instrumentation markets.

The HMC624LP4E belongs to Hittite's broadband digital attenuator product line, designed specifically for high-linearity, wideband RF gain control in infrastructure and test systems demanding precision, speed, and configurability.

FAQ

What is the minimum operating frequency of the HMC624LP4E?

The HMC624LP4E supports true DC-coupled operation down to 0 Hz when used with external AC-ground capacitors (e.g., 330 pF on ACG1–ACG6 pins) and bias tees on RF ports. Its specified performance begins at DC, enabling use in baseband and IF applications below 100 MHz without performance degradation.

Does the HMC624LP4E require external matching components?

No, the HMC624LP4E does not require external matching components. Its RF ports (ATTIN and ATTOUT) are internally matched to 50 Ω across DC–6 GHz. However, external DC-blocking capacitors (e.g., 330 pF) are mandatory on RF ports for DC-coupled operation, and AC-ground capacitors must be placed on ACG1–ACG6 pins per the datasheet layout guidelines.

How does the power-up state selection work on the HMC624LP4E?

The HMC624LP4E supports two power-up configuration methods: if LE is held low at power-on, the PUP1 and PUP2 pins determine the initial attenuation per the PUP truth table; if LE is high, the D0–D5 logic states set the power-up state. The selected state latches approximately 200 ms after power-up, ensuring deterministic behavior without host intervention.

Can multiple HMC624LP4E devices be controlled using a single SPI bus?

Yes, multiple HMC624LP4E devices can be daisy-chained using the SEROUT pin. Serial data applied to SERIN of the first device appears at its SEROUT pin after six clock cycles, allowing connection to SERIN of the next device. This enables full 6-bit control of N devices using only three MCU pins (SERIN, CLK, LE), reducing GPIO overhead in multi-channel systems.

What is the maximum RF input power the HMC624LP4E can handle continuously?

The HMC624LP4E has an absolute maximum RF input power rating of 28 dBm at +85 °C. Under normal operation at +25 °C, its input 0.1 dB compression point is +30 dBm across DC–6 GHz. For continuous operation, thermal derating applies: dissipation must stay ≤0.635 W at +85 °C, decreasing by 9.8 mW/°C above that temperature.