I am using a Stellaris EK-LM4F120XL for a project. The project includes an LCD module, servo motor, ultrasonic ranger and a numpad. The LCD, servo and ranger are rated at 5V operating voltage, and the Stellaris at approx. 3.3V. To have the project powered as a stand alone unit, I have a battery pack for 2x9V batteries. I will hook these in parallel to offer a longer running time. Then they will flow into a voltage-regulator, LM317, to provide 5V to the peripherals..
Then I will use this 5V source thru a non-inverting hex-buffer, CD4050BE, to then power the microcontroller.. I understand that no matter what voltage is input - the difference between Vcc and GND is output. Although, does that mean for a buffer you need to have a voltage-in, and a desired voltage-out - but also need to supply a Vcc voltage to maintain the desired output?
Therefore, if I have my 5V source from my regulator, do I really need to create circuitry using a resistor-divider or transistor voltage-drop, to get my 3.3V - then input this into the hex-buffer..? What a waste of current, no?
Why not utilise another voltage-regulator with voltage-divider resistors like I used to get my 5V..?
What about a single-channel linear-regulator - LP2950-N, of 3.3V variation..? Or LM2936-3.3...? Why use buffers at all then.. instead of regulators..?
I have diodes/resistors/PNP BJTs/opAmps on hand.. I am using transistors, BC548, to operate my 'loads' that are in parallel with diodes already.. And will ground everything to the same point - negative terminal of the powerpack..
To clear it up - I need 5V for all peripherals, and approx. 3.3V for the uController..
(I have circuit diagrams but cant add pics..?)