I was trying to find a resource online that would explain how to use the 4050 chip to shift between 5v and 3.3-3.9v levels. I have a few RTCs that I want to use (bq32000 from TI), however it operates from 3.0v to 3.6v at Vcc (maximum), and Vcc + 0.3 at all other pins. I'm assuming this means that the chip will operate at 3.3v levels (logic low is 0.3*Vcc, high is 0.7*Vcc) but please correct me if I'm wrong.
Regarding this, I have 2 questions:
a) Typical current draw for this chip is about 100uA, so would it be OK to use a resistive divider to provide Vcc to the chip? I understand this is not great practice for supply lines, but would it be suitable for a low current application such as this? I remember reading a post where GrumpyMike explained why a resistive divider would fail if too much current were drawn but I can't find that at the moment. If this is not appropriate, could I supply the chip with 3.3v through a pin on the 4050?
b) From looking at the application of the 4050 chip on the Sparkfun SD shield, it is not immediately obvious to me how to set the logic level of your output voltage. Am I correct in my understanding that the output voltage level will be equal to the voltage at Vcc of the chip?
On a side note, if someone could point me to a tutorial or some sort of resource that would give me a better understanding of how to use the 4050 and other buffers/level shifters.