Thanks everyone for the suggestions and information, this post stood out in particular based on what I have read in the last few hours:
I agree with Zeke...No voltage regulator should do this...it is a sure recipe for disaster.
Having said that.....most, if not all LDOs have strict output capacitor requirements.
So, I'm going to ask a silly question: did you check the stability plots in pages 19 and 20 of the datasheet? Does your output cap meet these requirements?
I have been reading more about this and I am not even sure that my capacitor does. I did not realize that the capacitor would have that much of an effect on the regulator operation. I will look into this further and do more testing. This also opens up the what happens with age/temp etc variables that will affect the capacitor over time/operation. Most introductions that I have read regarding regulators showed the basic circuit with some emphasis on selecting resistors to set the voltage. Today in addition to your comment I came across more information regarding capacitor properties and their effect on regulator operation.
The circuit is 16VDC in to the regulator with 10uF caps on the input and output on a breadboard. This is connected directly to the VCC pin of the parallax 32400 USB adapter board. I read that this is an acceptable way to power this, but there are variables here that can cause problems. One big one is that the 3.3V regulated output from this regulator circuit I am talking about is feeding into the output of the 32400 on board regulator. I ordered the straight adapter board with nothing other than XBee pin spacing to breadboard pin spacing to avoid these other variables.
With no load on the regulator I did not see these spikes and the spikes would only show up 1/3 of every connection to power.
I did not draft this circuit anywhere as it is 4 parts in total (2 caps, regulator, 32400), so I do not have anything to readily upload. If this cannot be imagined I will try draw something up. I ordered 2 more types of regulators, different caps, straight XBee adapter boards to try get rid of this problem.
As a general question though, how would you protect down stream devices from a regulator? I saw one circuit that used a zener as a voltage reference connected to a comparator which compared this to the voltage supply. The comparator controlled a series pass FET to turn off the voltage downstream if there was an over voltage condition.
I do not see zeners or TVS diodes working on their own since the curves show they dont turn on hard at a specific voltage. The 3.3V TVS could go up to 8V clamping depending on the current.
In case of regulator failure and/or overvoltage how would you protect? Does no-one worry about this since boards are rarely repaired anymore?
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I have LM317 on order and should be here in a day or so, I will look at Linear Technology parts and try some of them. Now that you mention soft start I recall reading some parts that had this (DC-DCs, was staying away from them ATM due to more complexity/part count) I will look into trying out these. LC filter and zener I will also investigate more. I am very interested to see if the zener can hack my circuit into working. I still want to check the capacitors etc to do it right, but I am curious how to overcome "edge case use" after due diligence.
Thanks for the good information and suggestions, I now know where to spend my efforts to learn more about this and how to do it right. Seriously though during prototyping until this setup the regulators *just worked* in the past. I am glad this has happened though because what I am learning from it all. Since this is the first time I had this happen with a regulator circuit I am looking forward to trying different parts/design/analysis and seeing how they make a difference.