I've just built up a batch of PCBs with several LM317 and LM337 regulators on them. As this thing will be in a hot environment, I wanted to avoid electrolytics so I used 10uF MLCC ceramic capacitors on the inputs and outputs of the regulators. Now that I have built it, all of the regulators oscillate!
I had thought that it was only LDOs (with the drain or collector of the pass device connected to the output) that would oscillate with low-ESR capacitors, but I now know that this also applies to some non-LDO linear regulators. Having seen the oscillation, I looked in the LM337 datasheet and sure enough it says it isn't stable with low-ESR capacitors. It does not even say what range of ESR it IS stable with. In the case of LDOs, I already had the policy of refusing to design in the ones that require some ESR without specifying what range is acceptable.
By experiment, for the LM337LM I have found that somewhere in the range of 50mOhms to 100mOhms added between the regulator and 10uF MLCC seems to just barely stop it from oscillating, without any other decoupling capacitors connected. I would use a somewhat higher value to get more phase margin. Adding these resistors is a pain because I have a lot of other MLCCs decoupling the same rails, so there is no nice place to hack in the resistors, especially since the board was not routed with this in mind. If I put the resistor between the regulator and the power plane, then there will be some interaction between the different circuit blocks as they would then share a significant common supply resistance at DC. Perhaps an inductor? Meh.
I guess there is a good reason why ADI can charge more for their AnyCap LDOs. I wonder if any of them is pinout compatible with the surface mount LM317MDCYRG3 and LM337LM that I have used.
Chris