Arduino Mega 1mA in sleep mode. Are you sure about that.
There are many parts on a Mega board that can't be put to sleep.
Some switching regulators have a very low quiescent current. 200uA for this one.
Not sure why you worry about a few mA quiescent current.
An average car battery could have a self discharge current of 20mA or more.
14V-5V step-down converter: >90% efficiency.
14V-5V linerear converter: 36% efficiency, plus the need to deal with lot of heat.
In most definitions of "efficient" the first option wins. In your definition of "efficient" the second option wins. That's an interesting new take on "efficient".
For low quiescent current, maybe 360 nA sounds better to you? I know, not your voltage range, just to show they exist. The second link on my quick Google search got one that wastes a lot more, all of 10 uA, but it gets quite close to your input voltage requirements.
Tnx for the answers!
My step down converter have 4-5mA qu current and this is too much assuming that my car is drawing only 12mA without my project.
My project include an arduino mega, which will go to sleep after 100 sec after the car is off(i said 1mA because i suppose it won't consume more then 1mA in deep sleep )
And there is a lm358 (from a 433mhz receiver) that is always running and i don't know what is it's current.
So, i currently have 2 MCP1702 5V http://ww1.microchip.com/downloads/en/DeviceDoc/22008E.pdf
250 mA Low Quiescent Current LDO Regulator
2.0 µA Quiescent Current (typical)
but those are rated for maximum +14.5V ( exactly how my car's alternator is rated for at maximum output voltage 14.5V)
I'll order MCP1703 5V version which will have a maximum of 16V, but i can only order them after 2-3 months
meanwhile i wanted to use those that i have.
I also search for the IC that wvmarle said, and there is no shop in my county that sell this item, only on aliexpress/ebay, but there they are very expensive plus the shipping 10 USD compared to 1 usd for x2 MCP1702 or MCP1703
I'm not so in into electronics and i don't know if the regulators that i have are "efficient" in giving my the power that i want but I only want to draw 3mA( in total, i think) and those LDO Regulator seems to be Cheap, easy to use and offering low quiescent current when i need it.
May they won't be so efficient when supplying 100mA to the arduino, but in that case, the car would be ON, so the alternator
Sorry for my bad english i hope you understand.