The plan is to have a RTD (Resistance Temperature Detector) measurement circuit, ATTiny85 for temperature reading plus few buttons and an LCD display on the same PCB.
The RTD circuit I've chosen is this one provided by Microchip, which will need 2.5V. ATtiny's operating voltage is 1.8-5.5V and LCD's 3.3V.
I'm thinking of using 3.3V for LCD and ATtiny85, and a voltage regulator like LM1117T-2.5/NOPB to convert 3.3V -> 2.5V.
Is this liniar voltage regulator overkill for a low-power current excitation circuit?
Can i use a simple voltage divider for this task?
Right now I have a 3.3V PCB power supply from Mean Well which I plan to use for everything in my circuit (ATtiny85, LCD, RTD circuit, buttons + 4x50mA leds)
Ok, from what i understand, the voltage divider ratio can change because is directly proportional with the load so it's a big no-no for a RTD circuit that needs a stable power supply.
Here's the plan B:
220V -> 9V or 12V wall wart
4.75...36V -> 3.3V for ATtiny, LEDs and LCD display (DC/DC 1A converter)
3.3V -> 2.5V for the RTD circuit (DC/DC 500mA converter)