The only drawbacks i would see would be potential increase in component count and tolerance of the components used to specify voltage desired.
I think the selection of regulators here is being over examined for what looks like a prototype. I am certain that there are more important things in this circuit besides the selection of regulators in series.
Of all the things that has gone wrong in my circuit designs, not one of them was due to regulator interaction in series.
they only become too big of an issue with a highly unpredictable load (simulated with an electronic load) and some switching regulators…
the regulators are well compensated and trimmed…but if problems does exist in the prototype then it’s time for a rewire…a prototype is a prototype… 
houta69:
The wall warts I have appear to be regulated as I measure ~12.1V without any load. So is this a triple whammy to have three regs in series?
You may have one of the new wall warts that use a switching power regulator. More efficient and much better regulation.
I think the selection of regulators here is being over examined for what looks like a prototype. I am certain that there are more important things in this circuit besides the selection of regulators in series.
I was about to say the same thing. If you don’t get past the power supply, what fun is it???
Getting back to ground planes… I’m certainly no expert, I just learned how to do a ground plane in Eagle about a month ago. But I’ve found that they make routing your ground nearly effortless. Just do a polygon covering the entire bottom layer and name it GND. Then anytime you need something connected to ground, just pop in a via, click ratsnest, and you’ve got it. You just need to avoid putting so many non-ground traces on that layer that they chop the plane into multiple segments.
But do be sure and read your datasheets in case you have something that says not to put it over a ground plane. I’m working with a pressure sensor that gives analog output and the manufacturer notes to use ground planes selectively. Actually, that’s not in the datasheet, it’s in a application note referenced from the datasheet. It’s got a section on PCB layout considerations for digital and analog circuits that looks pretty useful. The App note is Freescale’s application note AN1646, [“Noise Considerations for Integrated Pressure Sensors”, but take a look starting on page 5. It looks like pretty useful info for more than just pressure sensors.
Keith](http://www.freescale.com/files/sensors/doc/app_note/AN1646.pdf)
you must also consider return paths even when using ground planes…
the application notes is always a good place to look at…
BTW, here are some more links to look for grounding and EMC references…
http://www.devicelink.com/mem/archive/98/10/007.html
and Mark Montrose’s technical papers:
http://www.montrosecompliance.com/Html/ … apers.html
some may be very technical but Montrose generalized some of the rules to apply…
good luck…
a little bit off topic…
to anybody interested why the second regulator may be affected by the first regulator and vice versa,
here’s one note on the effect of the regulator (the simulations are not for series connected regulators, rather its output impedance, but you can notice why it’s possible that first regulator can interact with the second one)
Hello All -
I just wanted to post an update since so many people had offered their advice/suggestions to me. I ended up going with a solid ground plane on my board, routing all of my traces on the top layer and I kept the regulators in series. I had already begun preliminary code development and have started testing the basics of that with the board. So far everything has worked out well.
I realize that this is a mickey mouse project, but it has been a big step for me with regards to dealing with the hardware side of things and I feel like I’ve learned a considerable amount. Thanks much to all who have provided me with direction!