In the previous blog post we analyzed deeply the difference between High-Speed DACs and Fast Precision DACs, focusing on the challenges and the specific features for their corresponding applications.
In this blog post, the last one of the series, we will explore the key parameters of a Fast Precision DAC and the performance achieved with the state-of-the-art AD35xxR family. This family encompasses 6 parts:
Figure 1. AD355xR block diagram
Figure 2. AD354xR block diagram
The most relevant improvement of Fast Precision DACs compared to traditional Precision DACs is update time. The update time takes into account the time to transfer the data from the controller to the DAC, the time to process the data in the DAC and the time to settle the output to the desired voltage. Every effort has been taken to minimize the update time in AD35xxR family. By reducing the update time, the part is better suited for closed-loop where latency limits the reaction time, such as Hardware in the Loop (HiL).
Figure 3. Data transfer and settling time
The AD35xxR family also features configurable output voltage ranges, shown in Figure 4.
Figure 4. AD355xR block diagram
The AD35xxR family is not only designed for gaussian signals and HiL. It is also well suited for harmonic applications such as precision waveform generation. The high sampling rate allows generating very clean tones over a wider bandwidth, reducing the need to switch filters. Figure 5 presents the THD of the AD35xxR family.
Figure 5. AD35xxR Family THD
The AD35xxR family offers two precision modes that can be alternated without reconfiguration. Fast mode allows using 16-bit data words to maximize the update rate while Precision mode offers higher accuracy using 24-bit data words. The comparison between the two modes in terms of DNL and INL is shown in Figure 6.
Figure 6. AD35xxR DNL and INL comparing Fast mode and Precision mode
16-bit and 24-bit samples can be interleaved to enjoy the benefits of each one. For example, 16-bit samples can be used to produce a fast transition between two levels and then 24-bit samples can be used to produce a slower but more accurate voltage.
Additional information and design resources are available in the AD35xxR product pages and signal chain pages:
This blog is the last issue of a series of five posts on Precision Wide Bandwidth applications: