Analog Devices Inc. DC644A

Overview

DC644A from Analog Devices (formerly Linear Technology) is a high-linearity, wideband upconverting mixer IC designed for wireless infrastructure transmitters. It operates with RF output from 1300MHz to 2300MHz, delivers 15.9dBm typical input IP3 at 1.9GHz, integrates an on-chip RF output transformer, requires only a single 5V supply, and supports single-ended LO and RF operation - enabling compact, low-cost cable downlink and point-to-point radio designs.

For engineers reviewing the DC644A datasheet, DC644A pinout, DC644A application, or DC644A equivalent, key selection considerations include its 1.3–2.3GHz RF bandwidth, –41dBm typical LO-to-RF leakage, 4dBm input 1dB compression point, integrated LO buffer requiring –5dBm drive, and 16-lead 4mm × 4mm QFN package with exposed ground pad.

Technical Context

The DC644A implements a double-balanced mixer core driven by a high-speed, internally matched LO buffer, enabling use of low-power single-ended LO sources without external matching. Its IF port accepts differential inputs from DC to 400MHz and requires external 100Ω termination resistors to ground for proper biasing and LO leakage suppression.

An integrated RF output transformer provides broadband 50Ω impedance matching across 1300–2300MHz, eliminating external RF matching components. The device supports both low-side and high-side LO injection and features an enable pin with 2µs turn-on time and sub-10µA shutdown current.

Key Specifications

Pinout & Package

DC644A is housed in a 16-lead plastic QFN package (4mm × 4mm) with an exposed ground pad (Pin 17) that must be soldered to PCB ground for optimal RF performance and thermal dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LT5511, DC644A offers optimized performance below 2.3GHz with lower LO drive requirement (–5dBm vs –3dBm), while LT5522 serves a fundamentally different signal chain role and cannot substitute for DC644A in upconversion applications.

Availability

DC644A is available at Aetrix Electronics and suitable for wireless infrastructure transmitters, cable downlink systems, and point-to-point microwave radios requiring stable component supply, consistent RF performance across temperature, and long-term production continuity.

Supply support for DC644A 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, Inc. (including legacy Linear Technology products) is a global leader in high-performance analog, mixed-signal, and RF ICs, serving communications, industrial, automotive, and instrumentation markets with precision, reliability, and innovation.

The DC644A belongs to Linear Technology's high-linearity RF mixer product line, engineered specifically for demanding wireless infrastructure applications where spectral purity, power efficiency, and integration reduce system cost and size.

FAQ

What is the primary function of the DC644A?

The DC644A is a high-linearity upconverting mixer IC that translates differential IF signals (DC to 400MHz) to RF output frequencies between 1300MHz and 2300MHz. It integrates a double-balanced mixer core, LO buffer, and RF output transformer - enabling efficient, compact transmitter designs without external matching components. DC644A is optimized for wireless infrastructure and cable headend applications requiring low distortion and high spectral purity.

Does the DC644A require external RF matching components?

No, the DC644A does not require external RF matching components due to its integrated on-chip RF output transformer, which provides broadband 50Ω impedance matching from 1300MHz to 2300MHz. This eliminates discrete baluns and matching networks, reducing bill-of-materials count and layout sensitivity. DC644A supports both single-ended and differential RF output configurations directly from the die.

What LO drive level is required for optimal performance of the DC644A?

The DC644A requires a nominal –5dBm LO input drive level for optimal linearity and conversion gain. Its integrated LO buffer is designed to accept this level directly, supporting both differential and single-ended LO sources without external amplification or matching. Drive levels from –10dBm to 0dBm are within absolute maximum ratings, but –5dBm delivers the specified 15.9dBm IIP3 and –1dB conversion gain. DC644A maintains stable operation across this range with minimal gain variation.

How is the IF input biased on the DC644A?

The IF inputs (Pins 2 and 3) of the DC644A are internally biased and require external 100Ω resistors (0.1% tolerance recommended) connected from each pin to ground to set the mixer core bias current (~18mA per side). These resistors must be DC-isolated from the IF source via blocking capacitors. Proper resistor matching and symmetrical layout are critical to achieving the specified –41dBm LO-to-RF leakage. DC644A does not support AC-coupled-only IF interfaces without these terminations.

Is the DC644A pin-compatible with other Linear Technology mixers like the LT5511?

No, the DC644A is not pin-compatible with the LT5511 despite sharing the same 16-lead 4mm × 4mm QFN package outline. Pin functions differ significantly - for example, LT5511 uses dedicated VCC pins for different internal blocks in a non-interchangeable arrangement, and its enable logic threshold differs. While both devices target upconversion, DC644A requires separate VCC1/VCC2/VCC3 supplies and specific IF termination, making direct PCB replacement impossible without layout revision.