I used the Texas Instruments WEBENCH® to come up with another power regulator. This time I wanted 5V from a range of 6V to 18V. The initial testing is positive in that it gives a clean 4.92V from 5.5V to 18V (I did not push it higher than that since 18V is already over what I expect). Below 5.5, the system drops out. On the circuit I added the provision for an additional battery backup. The thought was for 4xAAA cells to provide a short-lived 6V. At this stage, I am not worried about the 0.08V discrepancy as I am not yet sure if some of my part substitutions had an effect.
What was interesting is that without load, anything below 6.7V would also show an unstable output. For the initial testing, it was easy to add a 9V battery connector instead of the 4xAAA cell holder. I can imagine the 6V battery pack can still be used once the module has a more permanent connection to the load.
I find using the WEBENCH® a great way to get an in-road on using some of these power devices. The generated design gives all details down to BOM and suggested layout. The simulated thermal images are also pretty neat.
For this design particular design, I took up the WEBENCH® feature and swapped out the 0401 parts for 0805 parts to simplify assembly.
I have to admit, it does not feel like my design. It is more like a kit to my specification. At best it is implementing the application note without having to calculate the specific RC values. Time will tell, of course, on how this design will stand up when the module is really put to work.