I need 5V 5mA for a sensor. I am using Li-ion battery so max voltage is 4.2V. My AVR is running of 3.3V.
I think it will be overkill to to use a Step-up IC like the max668.
I do not have any availble counters that i can do PWM on my AVR.
So what would be my best option? Could i generate a pulse some other way to get voltage doubler then regulting it using a zener?
I think this would be the best option, as i require very low current. And it can be done cheaply, on bread board.
The other option is to use a 8.4V cell, at the moment i am using 4.2V 1000mA. So i would use 8.4V 500mA. This way the size of cell stays the same.
But the only issue would be this, say my circuit takes 100mA,
Then with 1000mA, i could have 10 hours of life
but with 500mA its only 5 hours.
But could the power loss from 8.4V to 4.2V, also give me a power to run for the extra 5 hours like the 1000mA cell does.
To be honest i prefer to use 4.2V cells.