Analog Devices Inc. 117212-HMC624LP4

Overview

HMC624LP4 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 2.4 dB typical insertion loss at 3 GHz. It operates from single +3 V or +5 V supply and serves as a precision signal-level control element in cellular infrastructure, microwave radios, and test equipment.

For engineers reviewing the HMC624LP4 datasheet, HMC624LP4 pinout, HMC624LP4 application, or HMC624LP4 equivalent, key selection criteria include its dual-mode (serial/parallel) CMOS/TTL-compatible interface, user-selectable power-up state, ±0.3 dB attenuation accuracy up to 6 GHz, and RoHS-compliant 4×4 mm QFN package requiring no external matching.

Technical Context

The HMC624LP4 implements a broadband GaAs MMIC architecture with integrated on-die switching elements and off-chip AC-ground capacitors enabling near-DC operation. Its dual-mode control accepts either 6-bit parallel input (D0–D5) or 3-wire SPI-compatible serial input (SERIN/CLK/LE), with latch enable (LE) governing state update timing.

Power-up behavior is configurable via PUP1/PUP2 pins or D0–D5 inputs, latching within ~200 ms. The device features a serial output (SEROUT) for cascading, supports TTL/CMOS logic levels at both +3 V and +5 V, and maintains stable RF performance across −40 °C to +90 °C operating temperature.

Key Specifications

Pinout & Package

The HMC624LP4 is housed in a RoHS-compliant 24-lead 4×4 mm QFN package with exposed thermal paddle; 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 HMC624LP4E, the original HMC624LP4 offers Sn/Pb solder compatibility and lower reflow temperature tolerance, while QM11036 trades cascading flexibility for tighter supply constraint - making HMC624LP4 optimal for legacy mixed-technology RF assemblies needing robust serial control.

Availability

HMC624LP4 is available at Aetrix Electronics and suitable for cellular infrastructure, microwave radio, and test equipment applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for HMC624LP4 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 was a U.S.-based RF/microwave IC designer acquired by Analog Devices in 2014; known for high-performance GaAs and SiGe MMICs targeting wireless infrastructure and defense markets.

The HMC624LP4 belongs to Hittite's broadband digital attenuator product line, engineered specifically for high-linearity, low-distortion RF signal conditioning in 3G/4G/WiMAX base stations and instrumentation-grade test systems.

FAQ

What is the operating frequency range of the HMC624LP4?

The HMC624LP4 operates from DC to 6 GHz, supporting applications spanning baseband, IF, and RF bands. Its DC-coupled design-enabled by external AC-ground capacitors-allows use down to 0 Hz, while its GaAs MMIC architecture maintains consistent insertion loss, return loss, and attenuation accuracy across the full range. This makes the HMC624LP4 suitable for both wideband communications and precision test instrumentation.

Does the HMC624LP4 require external matching components?

No, the HMC624LP4 requires no external matching components. It is internally matched to 50 Ω across its entire DC–6 GHz operating range. However, external blocking capacitors (e.g., 330 pF) are required on ATTIN and ATTOUT for DC coupling, and AC-ground capacitors (ACG1–ACG6) must be placed close to their respective pins to ensure low-frequency stability. These are biasing/support components-not impedance-matching networks.

How does the power-up state configuration work on the HMC624LP4?

The HMC624LP4 supports two power-up configuration methods: if LE is low at power-on, PUP1 and PUP2 set the initial attenuation per the PUP truth table; if LE is high, D0–D5 determine the state. The selected value latches ~200 ms after power-up. This ensures deterministic startup behavior-critical in systems where undefined attenuation could cause overload or calibration failure. The HMC624LP4 does not default to zero attenuation unless explicitly configured.

Can the HMC624LP4 be used with a 3.3 V supply?

Yes, the HMC624LP4 supports both +3 V and +5 V supplies. At +3 V, typical supply current is 1.8 mA, and logic thresholds are adjusted accordingly (low: 0–0.5 V; high: 2–3 V). All RF specifications-including insertion loss, IP3, and switching speed-remain valid at +3 V per the datasheet's "Min. [3]" conditions. This dual-supply capability allows direct integration into mixed-voltage RF subsystems without level-shifting.

What is the purpose of the SEROUT pin on the HMC624LP4?

The SEROUT pin on the HMC624LP4 provides a serial data output that echoes the SERIN input after a 6-clock-cycle delay. This enables daisy-chaining multiple HMC624LP4 devices (or other compatible Hittite serial components) using a single microcontroller SPI bus-reducing GPIO count and simplifying firmware control. SEROUT is active only in serial mode (P/S = high) and is disabled in parallel mode, ensuring no signal contention during mode switching.