Analog Devices Inc. DC1885A

Overview

DC1885A from Analog Devices (formerly Linear Technology) is an evaluation board for the LTC5544 high dynamic range passive downconverting mixer, supporting 4GHz–6GHz RF input and 4.2GHz–5.8GHz LO injection. It delivers 7.4dB conversion gain, 25.9dBm IIP3, and 11.3dB noise figure at 5250MHz with 240MHz IF output, enabling WiMAX, public safety band, and military communications receivers.

For engineers reviewing the DC1885A datasheet, DC1885A pinout, DC1885A application, or DC1885A equivalent, this page provides verified layout details, test circuit configuration, IF transformer matching guidance (TC4-1W-7ALN+), component BOM (C1=0.6pF, L4=2.2nH), thermal management notes, and performance validation across –40°C to 105°C case temperature.

Technical Context

The DC1885A implements a standardized downmixer test circuit per Figure 1 of the LTC5544 datasheet, featuring 50Ω single-ended RF and LO inputs, differential IF outputs (IF+/IF–), and 4:1 IF transformer (TC4-1W-7ALN+) for 50Ω single-ended IFOUT at 240MHz. It supports both low-side and high-side LO injection configurations.

Board stack-up uses NELCO N4000-13 laminate (0.062" thickness), with dedicated ground planes for RF, LO, and IF sections. Critical RF/LO matching components (C1=0.6pF, C3=1.2pF, L4=2.2nH) are placed within 2mm of IC pins to minimize parasitic inductance and ensure >12dB RF/LO return loss across full frequency bands.

Key Specifications

Availability

DC1885A is available at Aetrix Electronics and suitable for WiMAX receiver design, 4.9GHz public safety band infrastructure, and 4.9GHz–6GHz military comms development requiring stable component supply and validated RF layout reference.

Supply support for DC1885A 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. (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and RF ICs, serving precision instrumentation, communications, and defense markets.

The DC1885A belongs to Analog Devices' evaluation board portfolio for RF signal chain components, designed specifically to accelerate prototyping and performance validation of high-frequency downconverting mixers in demanding receiver applications.

FAQ

What is the primary function of the DC1885A evaluation board?

The DC1885A evaluation board is a fully assembled and tested platform for characterizing the LTC5544 passive downconverting mixer. It implements the standard test circuit from the LTC5544 datasheet, including RF/LO matching networks, differential-to-single-ended IF transformation via TC4-1W-7ALN+, and thermal management for reliable operation from –40°C to 105°C. DC1885A enables rapid validation of conversion gain, IIP3, and noise figure at 5250MHz.

Which IF transformer is used on the DC1885A, and why is it specified for 240MHz?

The DC1885A uses the Mini-Circuits TC4-1W-7ALN+ IF transformer, selected for its 4:1 impedance ratio and optimized bandwidth covering 240MHz. This matches the typical IF output frequency shown in the LTC5544 datasheet's test circuit (Figure 1), where L1/L2 = 150nH resonates with the internal IF capacitance (1.7pF) to deliver peak conversion gain and low spurious content. For IF frequencies between 250MHz–500MHz, the datasheet recommends TC4-1W-17LN+ instead.

Can the DC1885A support both low-side and high-side LO injection?

Yes, the DC1885A supports both low-side and high-side LO injection as confirmed by the LTC5544 datasheet's AC Electrical Characteristics tables. Its fixed component values (C1=0.6pF, L4=2.2nH) provide broadband RF input matching across 4GHz–6GHz, while LO input matching (C3=1.2pF) covers 4.2GHz–5.8GHz. Performance metrics - including conversion gain flatness (±0.15dB), IIP3, and NF - are validated for both configurations on DC1885A.

What power supply requirements must be met when using the DC1885A with the LTC5544?

The DC1885A requires two independent supplies: VCC = 3.1V–3.5V (pins 5 & 7) for the LO buffer and bias circuits (typical current 96mA), and VCCIF = 3.1V–5.3V (pins 14 & 15) for the IF amplifier (typical current 98mA at 3.3V, 101mA at 5V). Using 5V for VCCIF increases RF input P1dB by 3.2dB (from 11.4dBm to 14.6dBm at 5250MHz), as measured on DC1885A with the LTC5544 installed.

How is thermal performance managed on the DC1885A evaluation board?

Thermal performance on the DC1885A is managed through direct soldering of the LTC5544's exposed pad (Pin 17) to a large copper ground plane on the NELCO N4000-13 PCB, achieving a junction-to-case thermal resistance (θJC) of 8°C/W. The board's layout isolates RF, LO, and IF sections with dedicated ground vias and minimizes thermal gradients. This enables continuous operation at 105°C case temperature, as validated in the LTC5544 datasheet's thermal performance graphs (Figure G03).