Analog Devices Inc. DC945A

Overview

DC945A from Analog Devices (formerly Linear Technology) is an evaluation board designed to demonstrate and validate the LT5572 high-linearity direct quadrature modulator for 1.5GHz–2.5GHz wireless infrastructure transmitters. It provides full RF, LO, and baseband interface access-including 50Ω AC-coupled single-ended LO/RF ports, DC-coupled differential I/Q inputs with 0.5V common-mode biasing, and on-board 100nF AC-coupling capacitors. The board supports W-CDMA, LTE, and multi-carrier PHS/GSM/CDMA systems.

For engineers reviewing the DC945A datasheet, DC945A pinout, DC945A application, or DC945A equivalent, this page delivers verified hardware configuration details, measured RF performance data (including ACPR, image rejection, and OIP3), layout guidance for thermal and RF grounding, and direct correlation to LT5572 electrical specifications-enabling rapid prototyping of direct-conversion transmitter stages in DCS, PCS, and UMTS bands.

Technical Context

The DC945A implements the LT5572 in a fully populated, impedance-matched configuration with external 49.9Ω termination resistors at all four baseband inputs (BBPI, BBMI, BBPQ, BBMQ), 100nF AC-coupling caps on I/Q paths, and optimized RF output matching using a series 3nH inductor and shunt 2.1pF capacitor per the LT5572's RF output model. Grounding follows strict RF best practices: the exposed pad (Pin 17) is soldered directly to a solid PCB ground plane for both signal integrity and thermal dissipation.

It integrates discrete decoupling (100nF ceramic capacitors at VCC pins 8 and 13), enables precise enable control via a pull-up resistor network, and maintains 50Ω characteristic impedance on LO and RF traces per Linear's recommended layout. The board operates across the full LT5572 supply range (4.5V–5.25V) and ambient temperature range (–40°C to +85°C), supporting validation of conversion gain (–2.5dB), OIP3 (+21.6dBm @ 2GHz), and image rejection (–41.2dBc).

Key Specifications

Availability

DC945A is available at Aetrix Electronics and suitable for wireless infrastructure development, RF front-end validation, and W-CDMA/LTE transmitter design requiring stable component supply, traceable evaluation hardware, and documented reference performance.

Supply support for DC945A 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 Linear Technology in 2017 and maintains full technical and supply chain support for legacy Linear evaluation boards and ICs.

The DC945A belongs to Linear's precision RF evaluation platform family, engineered specifically to accelerate time-to-test for high-performance direct-conversion modulators used in macrocell and small-cell base station transceivers.

FAQ

What is the primary function of the DC945A evaluation board?

The DC945A evaluation board is a fully assembled hardware platform designed to characterize and validate the LT5572 direct quadrature modulator. It provides accessible test points for RF output, LO input, and differential baseband I/Q signals, enabling measurement of key metrics including conversion gain, OIP3, image rejection, and ACPR under real-world conditions. Engineers use DC945A to verify LT5572 integration before committing to custom PCB designs.

Does the DC945A support DC-coupled baseband inputs as specified for the LT5572?

Yes, the DC945A supports DC-coupled baseband inputs per LT5572 requirements. Each of the four differential baseband terminals (BBPI, BBMI, BBPQ, BBMQ) is terminated with 49.9Ω resistors to ground to maintain the 0.5V common-mode voltage and prevent floating. External DC bias can be applied directly, and the board includes no blocking capacitors in the baseband path - preserving low-frequency response and enabling true DC-coupled operation as required by the LT5572 datasheet.

How is RF output matching implemented on the DC945A?

The DC945A implements RF output matching per the LT5572's recommended output network (Figure 5 in the datasheet): a 3nH series inductor and 2.1pF shunt capacitor are placed between the LT5572's RF pin (Pin 11) and the SMA output connector. This network compensates for the LT5572's frequency-dependent output impedance (e.g., 52.6+j0.5Ω @ 2GHz) to achieve optimal 50Ω return loss across the 1.5–2.5GHz band, directly enabling accurate power and spectral measurements of DC945A's RF output.

Is the exposed thermal pad (Pin 17) of the LT5572 connected on the DC945A?

Yes, the exposed pad (Pin 17) of the LT5572 is soldered directly to a large, solid copper ground plane on the DC945A PCB. This connection serves dual purposes: it ensures proper RF grounding for optimal S22 and noise performance, and provides critical thermal conduction to maintain junction temperature below 125°C during continuous operation - a requirement explicitly stated in the LT5572 datasheet and validated in DC945A thermal testing.

Can the DC945A be used to evaluate multi-carrier W-CDMA performance?

Yes, the DC945A has been used to generate published 1-, 2-, and 4-channel W-CDMA spectra (Figures 11–14 in the LT5572 datasheet), demonstrating ACPR of –67.7dBc at 2.14GHz. Its layout preserves signal integrity across the full 1.5–2.5GHz band, and its baseband interface supports simultaneous I/Q stimulus generation. Measured results confirm DC945A's suitability for evaluating adjacent channel power ratio, noise floor, and spectral regrowth in multi-carrier basestation applications using the LT5572.