Analog Devices Inc. AD8345ARE

Overview

AD8345ARE from Analog Devices is a silicon RFIC quadrature modulator operating from 140 MHz to 1000 MHz, delivering +2.5 dBm P1dB output power at 800 MHz with −155 dBm/Hz noise floor, 0.5° RMS phase error, and 0.2 dB amplitude balance. It functions as the IF transmit modulator in digital wireless transceivers, enabling direct QPSK/QAM modulation for W-CDMA, GSM, and digital TV systems.

For engineers reviewing the AD8345ARE datasheet, AD8345ARE pinout, AD8345ARE application, or AD8345ARE equivalent, key selection criteria include LO frequency range compatibility (140–1000 MHz), differential baseband input drive requirements (1.2 V_p-p @ 5 V supply), RF output return loss (−20 dB), sideband suppression (−48 dBc typical at 220 MHz), and enable timing (2.5 μs turn-on).

Technical Context

The AD8345ARE integrates a polyphase phase splitter to generate precise I/Q LO signals, two Gilbert-cell double-balanced mixers, and a differential-to-single-ended converter delivering 50 Ω DC-coupled RF output at VOUT. Its bias architecture uses a Δ-V_BE-based band gap reference controlled by the ENBL pin.

LO inputs (LOIP/LOIN) accept −10 to 0 dBm differential drive with −9 dB S11 when terminated via balun; baseband inputs (IBBP/IBBN/QBBP/QBBN) require external DC biasing to 0.7 V and support 80 MHz bandwidth at full-scale 1.2 V_p-p drive.

Key Specifications

Pinout & Package

AD8345ARE is housed in a 16-lead TSSOP_EP package with exposed paddle for thermal management. Pin assignments are validated per Analog Devices Rev. B datasheet Figure 2 and Table 3.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD8346ARE and AD8349ARE, the AD8345ARE provides the optimal balance of wideband operation (140–1000 MHz), low-noise modulation (−155 dBm/Hz), and moderate power consumption (65 mA), making it the preferred choice for mid-band infrastructure where frequency agility and EVM stability are prioritized over extreme bandwidth or peak output.

Availability

AD8345ARE is available at Aetrix Electronics and suitable for cellular base station transceivers, W-CDMA femtocells, digital TV broadcast modulators, and LMDS fixed wireless access systems requiring stable component supply across industrial temperature ranges.

Supply support for AD8345ARE 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 is a U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and RF ICs for precision signal processing applications.

The AD8345ARE belongs to Analog Devices' RF transceiver modulator product line, designed specifically for direct-conversion wireless infrastructure requiring high linearity, low phase noise, and integrated LO quadrature generation.

FAQ

What is the recommended LO drive level for optimal noise performance in the AD8345ARE?

The AD8345ARE achieves its lowest noise floor (−155 dBm/Hz) at an LO drive level of −2 dBm. Reducing LO power to −10 dBm increases the noise floor by approximately 0.3 dB, while exceeding 0 dBm degrades linearity. This −2 dBm level is specified with 50 Ω source impedance and applies to both differential and single-ended LO configurations. The AD8345ARE datasheet Figure 21 confirms this relationship across the 140–1000 MHz band.

How does the AD8345ARE handle baseband input biasing, and what happens if external biasing is omitted?

The AD8345ARE baseband inputs (IBBP/IBBN/QBBP/QBBN) are not self-biasing and require external DC biasing to approximately 0.7 V. If omitted, the inputs operate outside their characterized common-mode range (0.6–0.8 V), causing severe gain compression, increased distortion, and degraded EVM. The AD8345ARE datasheet Table 1 specifies 0.7 V nominal DC common level, and Figure 4 shows bandwidth collapse below 0.4 V or above 1.0 V. AC-coupled designs must include resistive divider or DAC-based bias networks.

Can the AD8345ARE be used below 140 MHz, and what performance trade-offs occur?

The AD8345ARE can operate down to 70 MHz, but sideband suppression degrades significantly: from −48 dBc at 220 MHz to −20 dBc at 70 MHz (per Figure 29). Phase error increases beyond 0.5° RMS, and LO leakage rises due to reduced quadrature accuracy in the polyphase splitter. While functional, sub-140 MHz use requires external LO nulling and compromises EVM in standards like IS95. The AD8345ARE datasheet explicitly states that specifications are guaranteed only from 140 MHz onward.

What is the purpose of the multiple ground pins (COM1, COM2, COM3) on the AD8345ARE, and how should they be connected?

COM1 grounds the LO phase splitter and buffers; COM2 grounds the differential-to-single-ended output stage; COM3 grounds the baseband V-to-I converters and mixer cores. These are separate internal ground nets to prevent coupling between LO, RF, and baseband sections. All must connect to a low-impedance, solid ground plane - not daisy-chained - to maintain isolation. The AD8345ARE datasheet Figure 28 shows direct star grounding, and Table 3 emphasizes that improper grounding causes increased LO leakage and degraded sideband suppression.

Does the AD8345ARE support single-ended baseband drive, and what external components are required?

The AD8345ARE requires differential baseband drive but supports single-ended inputs via external circuitry. A unity-gain differential amplifier such as the AD8132 or AD8138 must convert the single-ended signal to differential format while adding the required 0.7 V common-mode bias. The AD8345ARE datasheet Figure 30 provides a verified schematic using two AD8132 op amps with 49.9 Ω input termination and precision bias network. Without this conversion, single-ended drive causes >10 dB degradation in sideband suppression and EVM.