Analog Devices Inc. HMC685LP4ETR

Overview

HMC685LP4ETR from Analog Devices (formerly Hittite Microwave) is a BiCMOS MMIC double-balanced mixer with integrated LO amplifier, designed for RF-to-IF downconversion and upconversion in 1.7–2.2 GHz systems. It delivers 8 dB typical conversion loss, +35 dBm input IP3, and −8 dBm noise figure at 200 MHz IF, supporting LTE/WiMAX base station transceivers requiring high linearity and low power consumption.

For engineers reviewing the HMC685LP4ETR datasheet, HMC685LP4ETR pinout, HMC685LP4ETR application, or HMC685LP4ETR equivalent, key selection criteria include its 24-pin 4×4 mm QFN package, adjustable G_BIAS and LO_BIAS for linearity–power trade-offs, DC–500 MHz differential IF bandwidth, and compatibility with low-side LO injection at 0 dBm drive level.

Technical Context

The HMC685LP4ETR integrates a broadband RF balun, LO buffer amplifier, and double-balanced diode ring core in a single BiCMOS die. Its RF port is internally DC-shorted via balun, while differential IFN/IFP supports DC-coupled or AC-coupled operation up to 500 MHz.

LO isolation exceeds 30 dB across 1.5–2.2 GHz, and RF-to-IF isolation reaches 42 dB typical - critical for suppressing image and LO leakage in FDD transceivers. Bias control via G_BIAS (0–5 V) and LO_BIAS (via external R9) enables dynamic optimization of conversion loss and IP3 without hardware change.

Key Specifications

Pinout & Package

24-lead 4×4 mm QFN package with exposed thermal paddle; RoHS-compliant matte tin plating, MSL1 rating, and max reflow temperature of 260 °C. Ground paddle and all GND pins must be soldered to PCB RF ground plane for optimal thermal and RF performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar mixer applications.

Compared with HMC685LP4ETR, HMC684LP4ETR offers identical mechanical and electrical interface at lower frequencies, while ADL5801ACPZ-R7 trades bandwidth for reduced integration and higher loss - making HMC685LP4ETR optimal for 1.7–2.2 GHz LTE/WiMAX infrastructure where IP3 and conversion loss are critical.

Availability

HMC685LP4ETR is available at Aetrix Electronics and suitable for cellular base stations, WiMAX access points, and GSM/CDMA repeaters requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for HMC685LP4ETR 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 continues to manufacture and support its high-performance RF/Microwave portfolio.

The HMC685LP4ETR belongs to Hittite's BiCMOS MMIC mixer family, engineered specifically for wireless infrastructure applications demanding high linearity, low conversion loss, and integrated LO amplification in compact SMT packages.

FAQ

What is the recommended LO drive level for optimal performance of the HMC685LP4ETR?

The HMC685LP4ETR achieves best linearity and conversion loss balance at 0 dBm LO drive, with specified operation from −6 to +3 dBm. At 0 dBm, it delivers 8 dB typical conversion loss and +35 dBm input IP3. Lower LO drive increases conversion loss; higher drive improves IP3 marginally but raises current draw and risk of saturation.

Can the HMC685LP4ETR be used in zero-IF receiver architectures?

Yes, the HMC685LP4ETR supports zero-IF operation via its DC–500 MHz differential IFN/IFP ports. Its internal balun design and DC-coupled RF/LO paths eliminate need for external blocking capacitors, enabling true DC-coupled baseband interfaces when paired with appropriate ADCs or baseband processors.

How does G_BIAS adjustment affect the performance of the HMC685LP4ETR?

G_BIAS (pin 19) controls the mixer core bias current: at +2.5 V (nominal), conversion loss is ~8 dB and IP3 is +35 dBm; reducing G_BIAS to +1.5 V increases conversion loss to ~11 dB but lowers supply current by ~30 mA, while raising it to +3.0 V improves IP3 slightly at the cost of higher dissipation.

Is the HMC685LP4ETR pin-compatible with other Hittite mixers?

Yes, the HMC685LP4ETR is pin-for-pin compatible with the HMC684LP4ETR, differing only in RF frequency range (1.7–2.2 GHz vs. 700–1000 MHz). This allows reuse of PCB layouts and bias networks across multiple bands in multi-standard base station designs.

What thermal management is required for continuous operation of the HMC685LP4ETR?

The HMC685LP4ETR has a thermal resistance of 48.33 °C/W (channel-to-ground paddle). For continuous operation at max Icc (120 mA @ 5 V = 600 mW), maintain PCB ground paddle soldering with ≥6 thermal vias to inner ground planes; ambient must stay ≤+75 °C to keep junction <125 °C.