I have been wondering for a while. With cheaper LDO regulators I often see them advertise that you can use a ceramic output capacitor. In the datasheet examples they use them. But then they say things like "ESR for output capacitor should be between 15mOhm and 200mOhm. I understand there is some small resistance added by the trace to the capacitor but often it is theoretically < 1mOhm based on trace width and length thickness. I have used regulators like this and know it works but why would the manufacturer spec a minimum ESR?
Also in case people misunderstand, I know the ESR is required for feedback loop stability, I'm asking why a manufacture puts what I feel is contradicting information in their datasheet.
Below is an example of what i mean, it is from AP7311. The datasheet can be found here: Datasheet