DAC Essentials: A new blog series

digital-to-analog converter, or DAC, performs the opposite function of an analog-to-digital converter, or ADC. Duh, right? But, have you ever wondered exactly what’s going on inside that integrated circuit? Unlike other analog components, DACs are much less familiar to many engineers.

This is the first post in a new blog series from me and my buddy Tony Calabria on Analog Wire. A few times a month we’ll be discussing precision DAC specifications from the ground up. We’ll explain architectural differences, the key specifications, calibration and deglitching techniques, reference and output buffer circuitry, and application specific concerns.

On the surface, DACs may seem limited to only a few applications. For many designers, a DAC brings to mind AC signal generation or the legacy of Burr-Brown audio DACs.

While DACs are a common component in audio equipment (something’s gotta convert your MP3 collection to vibrations in your headphones, right?), they’re also found in the DC application space. In addition to audio, you’ll find DACs in wireless base stations, medical instrumentation, industrial communication, biasing networks, process control, and more. Some DACs are even used to calibrate other DACs and some are found inside SAR and delta-sigma ADCs! 

Many DAC architectures are simply networks of resistors and switches, or tap points, to generate specific voltages or currents. Some architectures are a little more complex and use delta-sigma bit-streams or current-steering toplogies to achieve strong AC specs and high-speed throughput. An output buffer is sometimes included on silicon to isolate the DAC from its load, and some architectures assume that a buffer will be provided external to the IC.

Because of process and price limitations in discrete components, DACs are primarily created as integrated circuits. On silicon resistor ratios can be more tightly controlled and offered at much lower prices than discrete solutions, while bringing many integrated features to the table. In the precision DAC space, we see variability across several critical parameters, including:

  • Resolution
  • Channel count
  • Update rate
  • Digital interface
  • Current and/or voltage outputs
  • Glitch energy & settling time
  • Zero-code error
  • Offset & gain error
  • Linearity (INL/DNL)
  • Peripheral features (GPIOs, Alarms, etc)

In our next post in this series, we’ll explore the ideal DAC to establish the most basic fundamentals. After that, we'll delve into the two primary DAC architectures: the string DAC and R-2R DAC. Be sure to check back every few weeks or subscribe to Analog Wire so you don't miss out!

Leave your comments in the section below if you’d like to hear more about anything I mentioned in this post, or if there’s a topic you’d like me or Tony to address in future posts. We’d love to hear from you! 

PS: You can click this link read the other posts in the DAC Essentials series.