My application has a 6-12V supply for "normal" operation, backed up by a pair of AAs. The AAs power a TLV61220 to generate a 3.0 or 3.3V MCU supply, and the 6-12V supply powers a TPS709 3.3 - 3.9V LDO. Since the TPS709 has built-in reverse-voltage protection to turn off the pass transistor when its output is higher than its input, it would seem that a diode is unnecessary when connecting it to the MCU rail - if the 6-12V source is removed, the TPS709 will disconnect itself.
My question is regarding the behavior of the TLV61220 when its output is forced to a voltage the same as or slightly above its nominal voltage as set by the feedback divider.
Let's say I have the TLV61220's divider set for 3.0V, and the LDO is providing 3.3V. Will the TLV61220 stop operating completely, or will it turn on its switch periodically, possible creating noise issues and unnecessary current drain? How about if the divider is set for 3.3V and I force it to 3.3V?
I know I could disable the TLV61220 when the 6-12V power is available, but that adds some system complexity, and if it's not necessary I'd rather avoid it.
