Editor’s note: We will be doing a number of blogs on Planet Analog in the coming months regarding web-based simulation tools in order to help designers to see what’s out there to get your designs to market as quick as possible with a minimum amount of de-bugging and re-design. We will provide a balanced view of the various tools. Jonathan Harris from Analog Devices has begun this effort with VisualAnalog in some previous blogs and he outlines their ADISimADC tool here as a glimpse of part of their extensive offering.
In the last blog Analog Devices Design Tools: VisualAnalog Part 2 I introduced MOTIF (Modeling Operation Through the Implementation of Features) which is in the new simulator engine residing inside of VisualAnalog. I mistakenly mentioned that it is replacing ADIsimADC, however, it is not replacing the face of the software. ADISimADC will remain intact, but through MOTIF the simulator engine has gotten revamped. As I mentioned, the purpose of the tool remains the same it’s just the implementation that is getting a slight overhaul. For more information on MOTIF please visit here. More information about ADISimADC can be found at AN-905. Last time we looked at using ADISimADC to simulate the AD9680 from within the Visual Analog tool. Now let’s look at the web-based evaluation tool. This does not require downloaded software to run as it is purely ran from the web.
The web-based ADISimADC tool can be accessed online here. Navigating to this web page will bring the user to the page that appears below in Figure 1. The simulator defaults to the first ADC on the list in the drop down box which in this case is the AD9467-250.
There are six important links to note near the top of the page: Instructions, Glossary, Parametric Search, Request New Model, Submit Feedback, and Print Results. The Instructions link provides a detailed set of instructions for how to use the web-based tool (which we’ll look at a little later). The Glossary link provides common terms concerning ADC parameters and performance specifications. The Parametric Search link allows the user to find an ADC to simulate based on performance criteria. The Request New Model link allows the user to send a request into Analog Devices asking for a model to be created for an ADC that is not yet available through the web-based tool. There is also a link to allow the user to Submit Feedback. Feedback is always welcome and helps Analog Devices to improve upon the tool and provide a better user environment and more useful tool. The last link allows the user to print the results from a simulation either to an installed printer. This can be to a pdf file or a hard copy print out from an installed printer. These links are highlighted in Figure 2.
So let’s get started using the web-based ADISimADC tool. To begin we have two ways to select an ADC to simulate. The drop-down box on the web page may be used to select a product to simulate or the user can perform a search to find a product based on encode rate, resolution, SNR, and SFDR. Next, the operating conditions need to be entered. The first step here is to select the desired type of simulation. There are four options for the type of simulation: Single Tone, Two Tone, Frequency Sweep, and Amplitude Sweep. Next, the input stimuli must be entered. The user must set the input signal amplitude and frequency, encode rate, and encode jitter.
Let’s look at an example with the AD9643-250. For this example we will set the simulation type to Single Tone, the input amplitude to -1 dBFS, the input frequency to 220.1 MHz, the encode rate to 250 MSPS, and the encode jitter to 0.06 ps.
Figure 3. Simulation Results for the AD9643-250
Now let’s compare our simulation results to the data sheet typical values. The simulation shows an SNR value of 68.39 dB (69.39 dBFS) compared to a value of 69.9 dBFS listed in the data sheet. This is a little more pessimistic because we used a higher value of encode jitter than what was used to generate the typical performance numbers in the data sheet. The encode jitter can be optionally adjusted to see the effects on the ADC noise performance. The simulated SFDR value is 87.32 dBc which is on par with the typical value of 85 dBc listed in the data sheet. The ENOB value generated by the simulator shows 11.05 bits which is in line with the data sheet typical value of 11.1 bits. Much like the simulator demonstrated within VisualAnalog, the web based simulator also provides results in line with the expected typical performance of the ADC. Notice also, that the simulator returns results for SINAD, THD, 2nd through 5th harmonics, worst other spurious, and noise floor.
We have now examined the ADISimADC simulator from within VisualAnalog as well as in web based form. The simulator can be used to provide a good approximation for ADC performance without having to purchase actual hardware. This is a great start to any new design. An ADC can be simulated and evaluated prior to ordering hardware to help ensure the user selects the best ADC to evaluate for their new system design. Making the ADISimADC tool available in web based form allows access to simulate various Analog Devices high speed ADCs from the web without the need to install the VisualAnalog software. From anywhere with an internet connection an ADC can be simulated. This allows a convenient as well as accurate simulation to be performed for the user that may be on the go or in need of a quick set of results. In today’s fast paced world, time is of the essence and this tool provides an ingenious way to simulate expected ADC performance.