[Al (astral highway)]

Please note from mfr data sheet, "....input voltage must remain typically 2.0V above output voltage even during the low point on the input
ripple voltage".

To protect against this happening (likely at switch-off), install reverse diode connected cathode to pin 1, anode to pin 3 of VR.

(Thanks to Ed Dinning for pointing this out to me recently. You'll see it on commercial designs using these voltage regulators.)