Maxim Integrated’s EE-Sim & OASIS ─ Quick and Efficient Power Supply Design
Thought ─ consideration are central to all elegant design. Even within what you can’t see, what runs the “engine” of electrical design, the power supply. For example, portable products are generally battery powered. However, the voltage from batteries can vary, and the circuits that need the power will generally have specific requirements needed to operate correctly. Voltage regulators are essential to provide stable, fixed voltages. These include linear regulators, switching power supplies, and charge pump circuits.
Fortunately, there are many companies that offer thousands of circuits to help with power supply design. Although this is a good thing, from my experience it can also make finding and choosing the correct power supply a daunting task.
To help with power supply design, Maxim Integrated offers a free design tool that will allow a user to choose a power supply IC, and upon entering the required voltage input and outputs, will automatically generate a working schematic that can be simulated and built. In addition, typical design trade-offs generally encountered can be tweaked to get the best result for one’s needs. These can include cost versus performance, efficiency versus size, and desired switching frequencies. The tool is available as an online simulator called EE-Sim from Maxim, see it after this jump.
To begin aiding in the process of choosing a power supply for a design, Maxim’s software tool includes a parametric search feature that will narrow down options based on a user’s requirements. For example, for a DC-DC converter design, the user would first define the type needed. This would be either an inverting, a step up, a step-down, or a step up/down. Secondly, the input and output voltages needed are chosen. At this point, the parametric search would have narrowed down the possible solutions greatly. However, if more filtering is needed, the user can also choose features that would be desirable from the power supply. These may include external sync, adjustable switching frequency, and current limiting, to name a few.
After a promising IC is chosen, the real magic begins to happen. A schematic can be created, displaying all the needed component values and connections to create a functional converter circuit. An example schematic created using the online EE-Sim is shown below for reference:
In addition, simulations can now be run on the circuit to evaluate the performance. Simulations available include Load Step, AC Loop, Steady State, Line Transient, Start Up, and Efficiency simulations. Depending on the simulation that is chosen to run, different general settings are available to assist with the simulation setup. These include simulation run time, initial conditions, and in the case of the load step simulation, pulse current characteristics (pulse amplitude and width). Furthermore, if an unrealistic or erroneous value is entered into one of the settings, the selection will show a warning message or turn red, indicating it needs to be reconsidered or corrected. The simulator will only run parts with inputs and outputs within its acceptable range. This can help save the user from themselves if the chosen part is not capable of handling the required load conditions.
When a simulation is chosen and run, data will be available to view in graphical plots. The plots will be opened in another web browser window labeled as “Webscope,” with different tabs showing different automatically generated plots. Continuing with the Load Step simulation as an example, four tabs are automatically generated. A switching tab, output tab, input tab, and IC tab. Any net in the generated schematic with a label on it will be available for viewing. The input and output tabs will display plots of current and voltages for the nets associated with the input and output of the circuit. Furthermore, the IC tab will show most of the voltage waveforms associated with the ancillary pins of the circuit, such as the REFIN, PGOOD, and EN pins. On the other hand, the switching tab will show waveforms associated with the switching node.
The Webscope tool is intuitive to work with and includes all the general features you would expect from a simulation tool. It includes the ability to add and delete waveforms, scale the horizontal and vertical axis to specific values, or auto-scale if desired, and zoom in and out of specific locations. Additionally, markers can be included, and plots can be downloaded, saved, or printed.
In my opinion, one of the more notable features of the tool is its ability to create reports. The report can be downloaded in a PDF format and will include all the design requirements entered for the schematic creation. Plus, the schematic is included as well as a BOM with all the links to the needed parts from Mouser. The user even has the option to include any plots of waveforms generated through simulations in the report if desired.
Aside from the online tool, Maxim Integrated offers a free version of an offline simulator called OASIS. OASIS is powered by SIMPLIS and SIMetrix simulating engines. SIMPLIS is an algorithm created specifically for handling switching power supply simulations. On the other hand, SIMetrix is a more general simulating algorithm built off of the SPICE simulator. The offline tools will not generate schematics for you as EE-Sim will, but there are reference designs available if a user needs a starting point. There are tutorials and references available to help newcomers get comfortable with the tools. Overall, Maxim Integrated is offering intriguing solutions to compete with LTPowerCAD and LTSpice simulation solutions.