I need to power some noise-sensitive mixed signal chips with both 3.3V and 1.8V. Noise sensitivity can be taken care of with 3.3V and 1.8V LDO.
The problem is, the chips need to be powered on all the time, and in standby mode I only have low-current 3.3V available that can only power the standby mode, but in power on mode I have plenty of 5V and 12V available.
So what would be best here, use boost converter on 3.3V standby to something larger, diode-or that with 12V, and buck it down to 3.6 and 2.1 for the LDOs?
Or should I just diode-or the 3.3V and 12V together, and use that for buck-boost to 3.6 and 2.1 for the LDOs?
Is diode-or good, or what else could be used for safe switching between power sources so that the chips can stay powered continuously?