Sleep mode and power regulator

inaki

I am trying to save some power in a remote controller that uses a SX28AC as the main chip.
I am using B-port wakeup control in order to take power down between keystrokes.

I use an LM7805 to convert 9V battery power to 5V which, in place, feeds my SX28AC.
My question is: is LM7805 wasting power even while I am in sleep mode ?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

pjv

Hi Inaki;

Most definitely, although the power wasted is reduced from the normal running condition. When the SX goes into sleep mode, its current consumption drops drastically, but you are still left with the idle current of the 7805. I believe there are other regulators out there that have a lower idle current, but offhand I don't know their numbers.

Cheers,

Peter (pjv)

Mike Green

Yes. The LM7805 is a very inefficient regulator. All regulators need to use some current for their own internal functioning (like voltage references) and the LM7805 is not particularly careful there. Use a low-dropout regulator with low quiescent current like the LM2931 or LM2940 or the Micrel MC2950.