Analog Devices Inc. AD9851BRSRL

Overview

AD9851BRSRL from Analog Devices is a CMOS 180 MHz direct digital synthesizer (DDS) with integrated 10-bit DAC and high-speed comparator, delivering phase-continuous sine-wave synthesis and low-jitter square-wave clock generation. It features 32-bit frequency tuning (0.04 Hz resolution at 180 MHz), 5-bit programmable phase modulation (11.25° steps), and 6× reference clock multiplication for flexible oscillator design in RF and communications systems.

For engineers reviewing the AD9851BRSRL datasheet, AD9851BRSRL pinout, AD9851BRSRL application, or AD9851BRSRL equivalent, this page provides verified functional specifications, validated SSOP-28 pin mapping, confirmed industrial-temperature operation (–40°C to +85°C), and real-world use cases including agile local oscillators, spread-spectrum clock recovery, and digitally controlled ADC encode generation.

Technical Context

The AD9851BRSRL implements a numerically controlled oscillator (NCO) core with 32-bit phase accumulator and proprietary angle-rotation algorithm to convert truncated 14-bit phase data into 10-bit DAC amplitude values-enabling high SFDR (>64 dBc at 1.1 MHz) without large ROM tables. Its DDS output drives an on-chip 10-bit DAC optimized for low glitch energy and dynamic performance.

Internal 6× REFCLK multiplier allows use of low-frequency crystal sources (e.g., 30 MHz) to generate 180 MHz system clock with minimal degradation in SFDR and phase noise; comparator supports <80 ps p-p jitter at 20 MHz output when driven by filtered DAC signal, and operates asynchronously via parallel (5×8-bit) or serial (40-bit) control interface.

Key Specifications

Pinout & Package

AD9851BRSRL is housed in a 28-lead Shrink Small Outline Package (SSOP), pin-for-pin compatible with AD9850, with exposed thermal pad not connected internally. Package dimensions: 10.2 mm × 5.3 mm × 1.75 mm (JEDEC MO-153).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar direct digital synthesizer applications.

Compared with AD9851BRSRL, AD9850BRSZ offers drop-in replacement at lower speed and cost, while AD9951YSVZ delivers superior spectral performance at the expense of power, package size, and compatibility-making AD9851BRSRL the optimal balance of integration, jitter, and SSOP footprint for industrial RF synthesis.

Availability

AD9851BRSRL is available at Aetrix Electronics and suitable for frequency-agile local oscillator design, spread-spectrum clock recovery, and digitally controlled ADC encode generation requiring stable component supply across industrial temperature ranges.

Supply support for AD9851BRSRL 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. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD9851BRSRL belongs to Analog Devices' DDS product line, engineered for compact, low-power, software-defined RF signal generation in communications, instrumentation, and radar subsystems.

FAQ

What is the maximum system clock frequency supported by the AD9851BRSRL?

The AD9851BRSRL supports a maximum system clock frequency of 180 MHz when the 6× REFCLK multiplier is disabled and a 5 V supply is used. At 3.3 V, the maximum clock drops to 125 MHz, and at 2.7 V it is limited to 100 MHz. These limits are specified over the full industrial temperature range (–40°C to +85°C) and are confirmed in the AD9851BRSRL datasheet's CLOCK INPUT CHARACTERISTICS table.

Does the AD9851BRSRL require external components for basic operation?

Yes, the AD9851BRSRL requires at minimum an external RSET resistor (typically 3.92 kΩ) to set DAC full-scale current, bypass capacitors on all supply pins (AVDD, DVDD, PVCC), and proper grounding separation between AGND and DGND. For comparator operation, a passive averaging circuit (two 100 kΩ resistors + 470 pF capacitor) is needed to generate the DC threshold voltage from IOUT/IOUTB, as shown in Figure 2 of the AD9851BRSRL datasheet.

Can the AD9851BRSRL generate quadrature outputs natively?

No, the AD9851BRSRL does not provide native quadrature outputs. However, two AD9851BRSRL devices can be synchronized via shared RESET and FQ_UD signals to generate precise I/Q pairs-one configured with 0° phase offset and the other with 90°-as demonstrated in Figure 7 of the AD9851BRSRL datasheet. This method guarantees stable 90° phase relationship across temperature and supply variations.

What is the purpose of the 6× REFCLK multiplier in the AD9851BRSRL?

The 6× REFCLK multiplier allows the AD9851BRSRL to generate an 180 MHz system clock from a low-frequency, low-cost 30 MHz crystal oscillator. This eliminates the need for expensive high-frequency oscillators while maintaining high SFDR and low phase noise-critical for cost-sensitive RF designs where board space and BOM count are constrained.

How does the AD9851BRSRL handle power-down mode?

The AD9851BRSRL enters power-down mode when the POWER-DOWN bit in the first control byte is asserted, reducing supply current to 4 mW at 2.7 V. In this state, the DDS core, DAC, and comparator are disabled, but the 40-bit input register retains its contents. Wake-up time from power-down is 5 µs, and the device resumes operation with no loss of programmed tuning or phase words upon exit.