I'm designing a power/charging circuit and I'm stuck on a little issue. The circuit is going to have 2 rechargeable 3.7V Lithium Ion batteries to power a separate circuit that requires 3.3 V to run. How can I make a this design with a virtual ground somewhere between 0-0.4 V? I cannot connect the batteries to ground with the rest of my circuit obviously, so I've been confused as to how exactly I can do this. Any help would be great!
Connect the batteries to the circuit ground, charge them with a grounded or a floating charger and use a buck (or linear) regulator to get from 3.7V to the 3.3V the circuit needs. The up side of doing it this way is that if your charger's big enough you could charge the batteries and run the downstream circuitry at the same time.