I have 3.3v regulated coming out of pmic but one of my chips has a weird requirement of 3.6-4.2v in its vbat pins. Now I don't work with electronics at all except for stuff I did in school a long time ago. This datasheet says it can take my input voltage and convert it to between 3.6-4.2 depending on the resistors I choose. I remember reading somewhere that it you can only step down with an LDO, if that's true then I can't use this. Do I use one of those buck boost converters instead? I really don't know what I'm supposed to do since I can't test any of this and have 0 experience.
EDIT:
Here are the datasheets of the chips I am interfacing.
Wifi:
– on page 10 it shows the voltage specs and current consumption for the vbat pin? For current, on page 11 it says typical current consumption, does this mean vbat has to meet typical current consumption needs for it to work? I really don't know.
Best Answer
No, a Low Drop Out Linear Regulator cannot be used to boost a voltage up. That specific one has a Drop out of 0.1 ~ 0.25 Volts, so the maximum V OUT is VIN - 0.25 Volts.
You need a Boost circuit. Depending on your specific current needs, there are different types of boost regulators that will work. A charge pump uses a few capacitors and will be the simplest for under 200 mA. Otherwise there are plenty of normal regulators that use an inductor and diode pair, with internal mosfet, that can be used.
TI and every other manufacturer have tools that basically design it for you.
The three other options, since you have a 5V power source in the first place, are:
Parallel the 5V to 3.3V PMIC with a 5V to 3.8V~4.0V LDO. Less complex, and no need to double up on 5V down to 3.3V, then up to 3.8V.
Change the PMIC to be 3.8V output, and use an LDO to get 3.3V from that.
See if you can just change everything to 3.6~3.8V. No more multiple regulators.