AD9854AST

Overview

The AD9854AST is a CMOS quadrature Direct Digital Synthesizer (DDS) manufactured by Analog Devices. It integrates two high-speed 12-bit digital-to-analog converters (DACs) and an ultrahigh-speed comparator with 3 ps rms jitter. The device supports a maximum internal system clock frequency of 200 MHz, enabling output signal frequencies up to 150 MHz. It features dual 48-bit programmable frequency registers and dual 14-bit phase offset registers for precise control. The AD9854AST operates on a single 3.3 V supply and is specified for the industrial temperature range of −40°C to +85°C. It utilizes a small 80-lead LQFP package.

Feature Summary

• Integrates dual 12-bit DACs for quadrature I/Q synthesis with programmable amplitude modulation.
• Includes an ultrahigh-speed comparator capable of generating agile square wave outputs with low jitter.
• Supports multiple modulation modes including FSK, BPSK, PSK, chirp, and AM via simplified serial or parallel interfaces.

Applications

• Agile quadrature local oscillator (LO) frequency synthesis in communication systems.
• Programmable clock generators requiring low jitter and fast frequency switching.
• FM chirp sources for radar and scanning systems.
• Test and measurement equipment requiring precise signal generation.

Procurement Notes

Verify the specific suffix AST against the manufacturer's current ordering guide to confirm the 200 MHz clock limit and package type. Ensure the procurement channel provides valid traceability documentation. Confirm that the component meets RoHS compliance standards as indicated in the datasheet revision history. Check for any obsolescence notices or lifecycle status updates from Analog Devices prior to finalizing orders.

Selection Notes

Select the AD9854AST when a maximum system clock of 200 MHz is sufficient for the application, offering a cost-effective alternative to the 300 MHz ASVZ variant. Ensure the design accommodates the 80-lead LQFP package dimensions and thermal requirements. Verify that the external reference clock source can support the required 4x to 20x multiplier settings if lower input frequencies are used. Confirm compatibility with the 3.3 V logic levels for the serial or parallel interface.

Part Context

The AD9854 series represents a family of highly integrated DDS devices from Analog Devices. The AST variant specifically denotes the version rated for a maximum internal clock frequency of 200 MHz, distinguishing it from the ASVZ variant which supports up to 300 MHz. Both variants share identical pinouts and functional architectures but differ in their high-frequency performance specifications. This part is designed for applications requiring quadrature signal generation with high spectral purity.

Replacement Considerations

The AD9854ASVZ is a direct pin-compatible replacement that offers a higher maximum clock frequency of 300 MHz. Designers should verify that the increased speed does not introduce unintended thermal issues or require changes to the PCB layout due to different power dissipation characteristics at higher frequencies.