Analog Devices Inc. AD9765AST

Overview

AD9765AST from Analog Devices is a 12-bit, dual-channel, 125 MSPS TxDAC+® digital-to-analog converter optimized for I/Q baseband signal synthesis in communications systems. It integrates two matched current-output DAC cores, on-chip 1.2 V reference, and dual-port/interleaved digital interface in a 48-lead LQFP package. Key confirmed specs: 12-bit resolution, 125 MSPS update rate, 0.1% gain matching, 75 dBc SFDR at 5 MHz output, and 380 mW power dissipation at 5 V.

For engineers reviewing the AD9765AST datasheet, AD9765AST pinout, AD9765AST application, or AD9765AST equivalent, this page delivers verified technical context, exact pin functions, real-world use cases in quadrature modulation and VDSL, and validated alternative parts with documented functional and application differences.

Technical Context

The AD9765AST implements two independent, segmented current-source DACs with proprietary switching to minimize glitch energy and maximize dynamic accuracy. Each DAC provides differential current output (IOUTA/IOUTB per channel) supporting both single-ended and transformer-coupled configurations, with nominal full-scale current of 20 mA and 0.1% inter-DAC gain matching.

Digital interface supports dual-port mode (independent WRT1/WRT2 and CLK1/CLK2) or interleaved mode (single high-speed data stream demuxed via MODE and IQSEL), enabling flexible I/Q data handling. Gain control is configurable via GAINCTRL pin for either independent resistor-based scaling or shared resistor setting of full-scale current.

Key Specifications

Pinout & Package

AD9765AST uses a 48-lead LQFP package (10 mm × 10 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are defined per Analog Devices Rev. G datasheet Figure 4.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel DAC applications.

Compared with AD9765AST, AD9767ASTZ offers higher resolution in identical form factor for improved SFDR in narrowband systems, while AD9744ARUZ trades integrated reference and power management for raw speed and compactness-making AD9765AST the optimal balance of precision, integration, and thermal efficiency for mainstream broadband communications.

Availability

AD9765AST is available at Aetrix Electronics and suitable for base station transmitters, VDSL line cards, quadrature modulator drivers, and medical ultrasound beamformers requiring stable component supply across long production lifecycles.

Supply support for AD9765AST 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 global leader in high-performance analog, mixed-signal, and DSP technologies, serving communications, industrial, and healthcare markets since 1965.

The AD976x family was designed specifically for high-fidelity, low-distortion I/Q signal synthesis in wired and wireless infrastructure-emphasizing matching, reference integration, and flexible digital interfacing for rapid system integration.

FAQ

What is the maximum clock frequency supported by the AD9765AST?

The AD9765AST supports a maximum update rate of 125 MSPS, as confirmed in the Dynamic Specifications table (Table 2) of the Rev. G datasheet. This applies to both dual-port and interleaved modes. Operation above this rate risks timing violations, degraded SFDR, and potential latch-up per Absolute Maximum Ratings. The AD9765AST achieves this rate with 3.5 ns minimum latch pulse width and 2.0 ns setup time, requiring careful PCB layout for signal integrity.

Does the AD9765AST include an internal voltage reference?

Yes, the AD9765AST integrates a temperature-compensated 1.20 V bandgap voltage reference (typical ±50 ppm/°C drift), accessible at the REFIO pin. This eliminates the need for an external reference in most applications. When used, the internal reference sets DAC full-scale current and improves system-level accuracy; however, it can be overdriven or bypassed with an external reference if tighter tolerance or different voltage is required.

How does the GAINCTRL pin affect full-scale current configuration on the AD9765AST?

The GAINCTRL pin on the AD9765AST selects between two gain control modes: logic high enables single-resistor configuration (one external resistor sets IOUTFS for both DACs), while logic low enables dual-resistor mode (separate resistors set IOUTFS independently per channel). This is documented in the Gain Control Mode section (Rev. G, p.22) and allows precise I/Q amplitude balancing or independent scaling without hardware changes.

Can the AD9765AST operate from a 3.3 V supply?

Yes, the AD9765AST operates from either 3.3 V or 5 V supplies for both AVDD and DVDD1/DVDD2 rails, as specified in Table 1 (DC Specifications) and Table 4 (Absolute Maximum Ratings). At 3.3 V, power dissipation drops proportionally-measured at 250 mW typical-while maintaining full 12-bit performance, 125 MSPS rate, and 0.1% gain matching. Logic thresholds adjust automatically per DVDD level.

What is the purpose of the SLEEP pin on the AD9765AST?

The SLEEP pin on the AD9765AST enables a low-power standby mode that reduces total power dissipation from 380 mW to 50 mW at 5 V, as stated in the Features list and DC Specifications table. In sleep mode, the DAC cores and reference are disabled while register contents are retained, allowing fast wake-up (<100 ns) without reinitialization. This is especially valuable in burst-mode systems like VDSL or TD-LTE where transmit activity is intermittent.