I am working on a remote gate opener setup. It will be powered via a 12v battery (12-13.5v) and charged via pwm solar charger at up to 14.5v. I would like to use the HT7333 LDO datasheet here
It has a max input voltage of 12v and I would like to avoid the magic smoke :)
I am looking for a way of reducing the voltage to a safe range so the LDO will work while not draining the 7 Ah battery much when on standby.
Background: The small micro controler will sleep for 1000ms then wake, turn on radio and listen for a signal for a few ms then back to sleep so the bulk of the time the current will be < 20 uA however when awake and opening gates its CPU:10 mA + 2xrelays 70~150 mA.
My thoughts so far:
LDO vs Switching Regulator - LDO as its sleep current is only 4 uA most SR are in the mA range and will empty my battery in winter. Also I have long range radio and the switching of the regulator will cause issues or make my PCB design more complex.
Use another LDO with voltage range i need - There are many designed for greater voltages but nothing in that class comes close to 4 uA current while CPU sleeps in fact most are 2-3 mA.
Use diodes to reduce voltage before the LDO - This seems the most promising as they will only consume power as it is drawn and not much if anything when not. However from the datasheets I have looked at it appears voltage drops on diodes are not static and change significantly based on the current load, so keeping it in a safe range could be tricky and I don't want so many that I have to extend the PCB (could fit in 4)
So I thought I would ask smarter people than I :) thanks in advance for your help.