AD9838ACPZ-RL

Overview

The AD9838ACPZ-RL is a low-power Direct Digital Synthesis (DDS) device from Analog Devices, housed in a 20-lead LFCSP_WQ package. It operates on a 2.3 V to 5.5 V supply and supports master clock rates up to 16 MHz for B-grade variants or 5 MHz for A-grade. The device features a 10-bit DAC with a 28-bit frequency register, enabling output frequencies up to 8 MHz with resolutions of 0.06 Hz at 16 MHz clocking and 0.02 Hz at 5 MHz clocking. Power consumption is 11 mW at 2.3 V. It includes an onboard comparator for square wave generation and a 3-wire SPI interface compatible with DSP standards.

Feature Summary

• Produces high-performance sinusoidal and triangular waveforms via a direct digital synthesis architecture.
• Integrates an onboard comparator to generate square waves suitable for clock generation applications.
• Supports independent analog and digital power supplies, allowing mixed-voltage operation such as 5 V analog and 3 V digital domains.
• Enables frequency and phase modulation through serial register loading or hardware pin toggling.

Applications

• Frequency stimulus and waveform generation
• Frequency phase tuning and modulation
• Low power RF and communications systems
• Liquid and gas flow measurement
• Sensory applications including proximity, motion, and defect detection

Procurement Notes

Verify the specific grade suffix when ordering, as the AD9838 is available in A-grade and B-grade variants with different maximum clock speeds. Confirm the package type is the 20-lead LFCSP_WQ. Ensure that the external resistor RSET is selected correctly to set the full-scale current, as this impacts the output compliance and power specifications. Check for moisture sensitivity handling requirements during storage and assembly.

Selection Notes

Select the B-grade version if the application requires a master clock speed up to 16 MHz; choose the A-grade for clocks up to 5 MHz. Consider the separate AVDD and DVDD pins if noise isolation between analog and digital sections is required. Evaluate the need for external filtering based on the Nyquist sampling theorem, particularly when using the onboard comparator for clock generation to suppress aliased images.

Part Context

The AD9838 is part of Analog Devices' DDS family, designed for power-sensitive applications. It shares architectural similarities with the AD9837 but offers higher performance metrics. The device is intended for industrial and communication equipment where size and power consumption are critical constraints. It utilizes a fully integrated design requiring minimal external components for basic operation.

Replacement Considerations

The AD9837 is a related component within the same product family. Verify compatibility regarding package dimensions and pinout if substituting. Note that the AD9837 may have different power consumption characteristics and clock speed limitations compared to the AD9838. Ensure that the replacement meets the specific frequency resolution and dynamic range requirements of the original design.

FAQ

How is the full-scale output current adjusted?

The full-scale output current is determined by connecting an external resistor (RSET) between the FSADJUST pin and AGND. The relationship is defined by IOUT FULL SCALE = 18 × FSADJUST / RSET, with FSADJUST being nominally 1.14 V.

Can the analog and digital sections be powered independently?

Yes, the AD9838 has separate AVDD and DVDD pins. They can be powered from different supplies, for example, AVDD at 5 V and DVDD at 3 V, provided the voltage difference does not exceed absolute maximum ratings.

What is the purpose of the onboard comparator?

The onboard comparator converts the sinusoidal DAC output into a square wave. This feature allows the AD9838 to function as a clock generator, though it is recommended to limit the output frequency to less than 33% of the reference clock to minimize aliased signals.