TIDUEV2 October   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Differences Between Audio DACs and Precision DACs
      2. 2.2.2 Right-Justified I2S to Daisy-Chained SPI Conversion
    3. 2.3 Highlighted Products
      1. 2.3.1 DAC11001
      2. 2.3.2 OPA1656
      3. 2.3.3 OPA1622
      4. 2.3.4 OPA2828
    4. 2.4 System Design Theory
      1. 2.4.1 Output Glitch
      2. 2.4.2 Sample Rate Dependence in Precision DACs
      3. 2.4.3 System Noise
      4. 2.4.4 DAC11001A vs DAC11001B
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 Required External Power Supplies
      2. 3.1.2 Jumper Definitions
      3. 3.1.3 Selecting I2S Source
        1. 3.1.3.1 USB I2S Source
        2. 3.1.3.2 SPDIF I2S Source
        3. 3.1.3.3 External PSIA I2S Source
    2. 3.2 Software Requirements
      1. 3.2.1 Installing the XMOS USB 2.0 Driver
      2. 3.2.2 Setting USB Sample Rate
    3. 3.3 Testing and Results
      1. 3.3.1 Measuring Total Harmonic Distortion and Noise
      2. 3.3.2 THD and THD+N Results
      3. 3.3.3 Measuring Dynamic Range
      4. 3.3.4 Dynamic Range Results
      5. 3.3.5 Measuring Signal-to-Noise Ratio
      6. 3.3.6 SNR Results
  10. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  11. 5Related Documentation
    1. 5.1 Support Resources
    2. 5.2 Trademarks
  12. 6About the Author

2.2.1 Differences Between Audio DACs and Precision DACs

There are many types of digital-to-analog converters (DACs) in the marketplace. These include general-purpose voltage-output DACs, highly specialized DACs such as audio DACs, and high-precision DACs like the DAC11001A. There are various architectures for these DACs. Most DACs use a precision resistor architecture like a string divider or R-2R ladder. More specialized DACs feature high-frequency switching architecture like a pulse-width modulator (PWM) or a delta-sigma modulator.

Early audio DACs primarily featured R-2R ladders, but as digital processes improved, multi-segmented delta-sigma architectures began to replace R-2R designs in most products.

There are positive and negative aspects to both of these architectures. For example, R-2R resistor ladders require very precise resistors to be integrated into the design, which can add cost. In addition, most resistor ladder type designs have code-to-code dependent errors, such as glitch, that can impact AC performance.

Delta-sigma designs integrate many forms of error averaging to reduce the impact of errors, reducing the need for precise analog components. However, these DACs require a higher frequency main clock to drive the over-sampling circuit. This clock results in noise at higher frequencies, while R-2R architectures have a flat noise profile.

Practically speaking, using a precision DAC in an audio DAC application can present some difficulties. First, precision DACs require a low-noise and precise reference voltage. Next, precision DACs lack digital features like volume attenuation with zero-crossing detection. And finally, precision DACs do not accept standard I2S inputs. This means that some digital logic must be added to the design to convert I2S to SPI.

This reference design compares the performance of the DAC11001A and DAC11001B. The DAC11001B features better THD+N performance at higher frequencies compared to the DAC11001A through a more advanced track-and-hold circuit. This circuit, along with the benefits and limitations, are described in Section 2.4.1 Output Glitch.