I know this question has been covered multiple times already; but as far as my reading goes I couldn't get any clear answers yet.
I am building a circuit based on a LiPo input source (4.2V to 3.3V) and I plan to shut-off any power withdraw at 3.3V in order to save the LiPo lifetime. (using voltage comparator on EN pin). The maximum current draw is around 500-600 mA, but for 80-90% of the time, the system will be on lower power mode (around 100mA). The operating voltage is 3.3V for as long as possible; until the LiPo voltage reached 3.3V (bottom discharge limit)
Therefore the dilemma and if I got my reading correct, so far this is what I understood. Under high load it is not favorable to use an LDO because of the increase of drop-out voltage; however it seems that a DCDC step-down would do the job perfectly. But according to my case I would like to have a second opinion; is there any reason to use one or another ?
DCDC Step-down : http://www.ti.com/lit/ds/symlink/lm3671.pdf
edit : In addition; what do you think about the benefit of using an LDO that would not track bellow 3.3V and therefore get rid of the voltage reference? As opposed to the DCDC that will track voltage well bellow 3.3, hence the need to shutdown system.