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SMS6.22 hints and tips

Thank you for downloading SMS6.22 for the stand alone design of our Simple Switchers®. This version now adds the LM2698 boost Simple Switch®. This part runs at 600kHz and 1.25MHz.

I wanted to provide you with some of the hints I feel would be useful when designing with this software. This program is designed to run in a Java environment. It uses a Java Virtual Machine to run so you do not need to install Java as a separate application. You will see what looks like a DOS window with "SMS6.22" as the task bar label. This is the Java VM. This window will have various messages and text and warnings scrolling across it. Do not be concerned by any of the warnings. The contents of this window are useful only if the software bombs. In the future we will figure out how to suppress this window and it will go away.

I have run this software on a 200MHz Pentium Pro with NT4.0 and on a 650MHz Win98 machine. Compared to version 6.2, the speed has been improved significantly.  The software will provide you with a design, but you should click on "Operating Values" to make sure there are no warnings regarding phase margin (stable operation). Most often, designs with low phase margin occur when using the LM259x and LM259xHV series of products. To eliminate the stability problems, use a -ADJ part and set the Cff capacitor to about 2.2nF to 10nF. For high output voltage (>12V), select a cheaper output capacitor with higher ESR. You may not find one in the list of choices, so check "Custom" and input an ESR > 300mohm. You may ask why I can tell you this here but not have it implemented in the software and I can assure you we are working on this. If you are using the LM259x products at Vin<=40V, then try the SMS4.3 software. It was the original and runs very clean. We are working out functionality bugs as we move to the new software platform. We are continuing to try and update our component databases and improve functionality. In this release we have added the ability to display the Bode plot. Check the "View Plot" at the top of the Operating Values page.

One bug I know about is as follows. If you click the "New Design" button before you have done any designs at all, the software will lock. Also, on some systems, the software can try to grab memory until the software starts to operate erratic. Maximizing the plot window has always been a problem on SMS and WebSIM.

One feature not yet documented is the ability to run a plot with one set of components and then change components and run the plot again.  The original plot window will remain available and you can compare the two to see how your changes effected operation.

Jon Cronk
Power Applications Manager



SMS4.3 hints and tips

SMS4.3 provides solutions for LM259x buck regulators for Vin<=40V and boost/flyback converters using the LM258x regulators. This software runs faster and has some features not provided in SMS6.2. One of these features is a good help section which can be accessed by pressing "F1". However, this version will not provide solutions for LM267x or LM259xHV products. Hint: If you get a warning about "Insufficient Phase Margin" for a step down application, try using the -ADJ part. You select the -ADJ part by setting the output voltage required to 5.01V versus 5.0V. The software is literal and will select the -ADJ part and add a feed forward capacitor. It you plan a SMT design this is almost mandatory.









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