battery-operatedboostldo
I'm working on a project that requires 3.3V from a pair of double AAs. I had thought that LDOs were always buck and if you needed boost you had to use a switching regulator. While doing some research for this project I came across the TPS736 line of LDOs from TI and now I'm confused.
http://www.ti.com/lit/ds/symlink/tps736.pdf
Reading the datasheet leads me to believe that I can get 3.3V from 2 AAs as they run down to the minimum input voltage of 1.7V. Am I reading that right?
Solderless breadboards are useless for prototyping circuits over a few hundred kHz. For high frequencies, you need to construct your prototype circuits "deadbug" style over a copper clad ground plane, like so:
I think it's nothing to do with the MOSFET- the CR2477 simply has too much internal resistance to drive enough current to run your circuit. As the battery terminal voltage drops, your boost regulator will try to draw more and more current to keep the output voltage stable and at some point cannot work. According to the datasheet, the voltage is starting to drop substantially even at 1mA.
That is typical for lithium coin cells.
Best Answer
At the bottom of Table 6.5, on page 6 of the datasheet, it says:
(1) Minimum V\$_{IN}\$ = V\$_{OUT}\$ + V\$_{DO}\$ or 1.7V, whichever is greater.
So V\$_{IN}\$ cannot be less than V\$_{OUT}\$. So it is a regular LDO.
The datasheet is not written very well.