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ADP667 latching up

Question asked by amirnaser on Jan 11, 2017

Hello. I am trying to build an adjustable power supply from a 9-V alkaline battery input, using ADP667. Everything seems to work except that the 10-uF output capacitor recommended by the datasheet drives the chip into a latch-up state thus dropping the input and output voltage, loading and killing the battery, and heating up the chip. It does not matter whether electrolytic or tantalum; the chip does simply not like anything in the uF range (have also tried 1 uF with the same outcome). Without a cap, the average voltage would be fine, but the time waveform is contaminated with high-frequency ripple. A 220-nF output cap, however, seems to eliminate the ripple and maintain the functionality. I thought that maybe the input voltage must also be bypassed by a, say, 10-uF, cap, but that did not help. In fact it made things worse.


Any thoughts?