I'm making a custom PCB that will be controlled by an Arduino Due. The Arduino Due provides 5V, 3V3, and a GND pin. I'm going to use this for most of the chips, and I will use a 9V battery or maybe even a separate power supply for the voltage reference and opamps.
1. Will the behaviour/output of opamps and voltage regulators/references such as the MAX6325 change appreciably with some droop in power supply voltage (e.g. from a battery?)
2. For every component on my schematic, I have a +power pin, and at the other power pin I put a GND there. However, some components on my PCB will be powered by a battery. The second terminal of the battery has to be connected somewhere... so how do I reconcile this? The MAX6325 has a GND pin, so I guess it wants to be connected to the same ground as all my other logic chips, and the return current will go out through that pin.
3. A DAC, a MAX5318, says I can connect a pin called AVSS to either a negative voltage power supply ~-1V or GND. I heard that the negative power supply is needed if you want the DAC to output negative voltages. But the datasheet never said anything about this. From what I can gather, it might not make a difference. Is this true/plausible?