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AD9731 10-Bit DAC: Specs, Replacements and Procurement Risks

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Quick-Reference Card: AD9731 at a Glance

Attribute Detail
Component Type 10-Bit, 170 MSPS Bipolar DAC
Manufacturer Analog Devices
Key Spec 170 MSPS Update Rate with 3.8 ns Settling Time
Supply Voltage +5V and -5.2V (Bipolar)
Package Options 28-Lead Flatpack (CDFP28)
Lifecycle Status Obsolete / Restricted Availability
Best For Aerospace, Military, and Demanding Communications Systems

1. What Is the AD9731? (Definition + Architecture)

The AD9731 is a 10-bit, 170 MSPS bipolar Digital to Analog Converter (DAC) from Analog Devices that delivers high dynamic performance and fast settling times for aerospace and military applications. While modern mixed-signal designs heavily favor single-supply CMOS architectures, this component relies on a robust bipolar process to achieve exceptional linearity and waveform reconstruction capabilities at high frequencies.

1.1 Core Architecture & Design Philosophy

Internally, the AD9731 is designed around a high-speed bipolar core rather than standard CMOS. This architectural choice enables its incredibly fast 3.8 ns settling time (to 1/2 LSB) and maintains strong Spurious-Free Dynamic Range (SFDR). The manufacturer integrated an internal voltage reference, saving engineers from allocating board space for an external precision reference. The inputs are TTL and High-Speed CMOS compatible, allowing it to interface seamlessly with standard digital logic families despite its bipolar analog heart.

1.2 Where It Fits in the Signal Chain / Power Path

The AD9731 sits at the very end of the digital signal chain. It typically acts as the bridge between a high-speed FPGA or DSP and the analog transmission path. It receives a parallel 10-bit digital data stream and converts it into an analog current or voltage, which is then usually fed into an RF upconverter, power amplifier, or directly to an antenna in Direct Digital Synthesis (DDS) base station applications.


2. Electrical Characteristics: The Numbers That Matter

2.1 Power Supply & Consumption Profile

The AD9731 requires a bipolar power supply, specifically +5V and -5.2V rails. It dissipates 439 mW of power when operating at its full 170 MSPS update rate. Why it matters: In modern designs, generating a clean -5.2V rail requires dedicated inverting switching regulators or charge pumps, which complicates the power tree and increases the BOM count compared to modern single-supply 3.3V DACs.

2.2 Performance Specs (Speed, Accuracy, or Efficiency)

This DAC offers a 10-bit resolution at a 170 MSPS update rate. Its Wideband SFDR is specified at 66 dB at 2 MHz and drops to 50 dB at 65 MHz. Why it matters: The 66 dB SFDR at lower frequencies ensures high signal purity for precision waveform generation, but engineers must account for the 16 dB degradation as the output frequency approaches 65 MHz, which may require tighter analog filtering downstream.

2.3 Absolute Maximum Ratings — What Will Kill It

Operating this part outside of its thermal and electrical limits will result in catastrophic failure. * Operating Temperature: The military/aerospace grade (0713F) is rated for a strict -55°C to 125°C. * Supply Voltage Limits: Bipolar components are highly sensitive to power sequencing and overvoltage. Applying the +5V rail without the -5.2V rail (or vice versa) can cause internal latch-up. Refer to the official AD9731 datasheet for exact maximum voltage tolerances.


3. Pinout & Package Guide

3.1 Pin-by-Pin Functional Groups

Pin Group Pins Function
Power +5V, -5.2V, GND Bipolar analog and digital supply rails
Digital Inputs D0 to D9 10-bit parallel data bus (TTL/CMOS compatible)
Output IOUT, /IOUT Differential analog current outputs
Control CLK, REF Clock input and internal reference pins

(Note: Exact pin numbering varies by package. Refer to the official datasheet for the complete layout.)

3.2 Package Variants & Soldering Notes

Package Pitch Thermal Pad? Soldering Method
28-Lead Flatpack (CDFP28) High-density No Hand-soldered or specialized reflow

The 28-lead flatpack is a classic military/aerospace package designed for high-vibration environments. Soldering Note: Flatpack leads are fragile and typically require custom lead-forming tools and highly controlled manual soldering or specialized reflow profiles to meet MIL-STD requirements.

3.3 Part Number Decoder

  • AD9731: Base series component.
  • 0713F: Indicates a specific military/aerospace-screened variant, packaged in the 28-lead flatpack, subjected to rigorous environmental and burn-in testing.

4. Known Issues, Errata & Real-World Pain Points

Problem: Obsolete / Restricted Availability * Root Cause: As a legacy bipolar component, production yields and demand have dropped, leading to obsolescence or restricted distribution channels. * Recommended Fix: For new designs, migrate to newer high-speed DACs. For legacy maintenance, consult specialized aerospace distributors for NCNR (Non-Cancellable, Non-Returnable) stock.

Problem: Complex Power Requirements * Root Cause: The underlying bipolar architecture inherently requires dual rails (+5V and -5.2V). * Recommended Fix: Use dedicated bipolar power management ICs (PMICs) to generate the negative rail cleanly, or redesign the board to utilize modern single-supply alternatives to simplify the power tree.

Problem: High Component Cost * Root Cause: The military/aerospace screened version (AD97310713F) undergoes expensive MIL-SPEC testing, driving the unit price above $4,000. * Recommended Fix: If designing a prototype or a non-flight test rig, utilize commercial-grade variants like the AD9731BRS to drastically reduce BOM costs.


5. Application Circuits & Integration Examples

5.1 Typical Application: Direct Digital Synthesis (DDS)

In a DDS application, the AD9731 acts as the core waveform generator. A high-speed FPGA calculates sine wave values and pushes them to the DAC's 10-bit parallel bus at up to 170 MHz. The differential analog outputs (IOUT and /IOUT) are typically routed through a 1:1 RF transformer to convert the differential current into a single-ended voltage, followed by a steep low-pass reconstruction filter to remove sampling aliases before the signal reaches the RF mixer.

5.2 Interface Example: Connecting to a Microcontroller / FPGA

Because the AD9731 uses a parallel interface operating at 170 MSPS, it is almost exclusively driven by an FPGA or a high-speed DSP, not a standard microcontroller like an Arduino or STM32. The interface requires precise clock alignment.

// Pseudocode for FPGA parallel data generation
always @(posedge clk_170MHz) begin
    if (enable) begin
        dac_data_out <= waveform_memory[address_counter];
        address_counter <= address_counter + 1;
    end
end
// Note: Ensure setup/hold times for D0-D9 align with the DAC clock pin.

6. Alternatives, Replacements & Cross-Reference

6.1 Pin-Compatible Drop-In Replacements

Part Number Manufacturer Key Difference Compatible?
AD9721 Analog Devices Older generation, slightly different dynamic specs ? Yes

6.2 Upgrade Path (Better Performance)

If redesigning a military or aerospace board, engineers should look at the Teledyne e2v EV12AQ600 or the STMicroelectronics RHF1201. These offer vastly superior sampling rates and radiation tolerance, though they require a complete schematic and PCB layout overhaul due to different footprints and power requirements.

6.3 Cost-Down Alternatives

For cost-sensitive, non-aerospace applications, the Texas Instruments DAC5652 provides a modern, dual 10-bit 275 MSPS alternative that operates on a much simpler 3.3V single supply, drastically lowering overall system cost.


7. Procurement & Supply Chain Intelligence

  • Lifecycle Status: Obsolete / Restricted. This part is incredibly difficult to source for new designs.
  • Typical MOQ & Lead Time: Highly variable. Due to its restricted aerospace nature, lead times can exceed 52 weeks if not in stock at specialized brokers.
  • BOM Risk Factors: Extreme. This is a single-source, legacy component with specialized packaging. Relying on it for new designs poses a severe supply chain risk.
  • Recommended Safety Stock: If maintaining legacy military hardware, procure enough stock for the entire expected lifespan of the equipment immediately.
  • Authorized Distributors: Only purchase through authorized mil-spec distributors (e.g., Rochester Electronics or specialized defense contractors) to avoid counterfeit ICs.

8. Frequently Asked Questions

Q: What is the AD9731 used for? The AD9731 is primarily used in aerospace and military devices, demanding communications systems, Direct Digital Synthesis (DDS), high-speed imaging, and base stations.

Q: What are the best alternatives to the AD9731? The most direct equivalent is the pin-compatible AD9721. For modern upgrades, engineers should evaluate the Teledyne e2v EV12AQ600, STMicroelectronics RHF1201, or the TI DAC5652.

Q: Is the AD9731 still in production? The AD9731 is widely considered obsolete or highly restricted. Procurement is difficult, and it is not recommended for new designs.

Q: Can the AD9731 work with 3.3V logic? The AD9731 features TTL and High-Speed CMOS-compatible inputs. While it can often accept 3.3V logic levels as "HIGH", you must verify the exact V_IH and V_IL thresholds in the AD9731 datasheet to ensure reliable triggering at 170 MSPS.

Q: Where can I find the AD9731 datasheet and evaluation board? Due to its legacy and restricted status, the official datasheet and any remaining evaluation boards must be sourced directly from Analog Devices' legacy archives or authorized aerospace distributors.


9. Resources & Tools

  • Evaluation / Development Kit: Legacy AD9731-EBZ (Check broker availability)
  • Reference Designs: Analog Devices legacy application notes on high-speed DAC interfacing.
  • Community Libraries: FPGA Verilog/VHDL reference designs for parallel DAC driving.
  • SPICE / IBIS Model: IBIS models for high-speed signal integrity simulation (available via manufacturer archives).

AD97310713F Documents & Media

Download datasheets and manufacturer documentation for Analog Devices AD97310713F.

AD97310713F PCB Symbol, Footprint & 3D Model

Analog Devices AD97310713F

Analog Devices

DAC 1-CH Segment 10-bit 28-Pin CFPAK Tray

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