This circuit shows how to add a 1st regulator to a source that already has a step for this purpose. The circuit was found in an American power supply documentation.
Combining an Ultra-Low Power MCU with an 802.15.4 Radio, the SAM R30 Enables Long-Lasting Battery...
This comparator with two Texas Instruments operators was obtained in a company application manual....
August 2017 - Mouser Electronics already has the Connect One Pico WiReach ™ SMTS Pico modules...