Hi, all!
I'm working at a project where I have a CR2450 battery(3v) and my circuit is 2.5V(10mA)
I'm trying to use LM317LZ but its drop voltage is about 1.5~1.8 so its not working.
Does anybody know a "easy to find on market" a regulator?
It can be fixed or adjustable voltage that provides 2.5V from a 3V?
Any suggestion will be apreciated.
Thabnk you very much.
BR
That's tough... How accurate does it have to be?
A simple silicon diode will drop 0.5 - 0.7V (probably closer to 0.7 at 10mA). So, if you just need "around" 2.5V unregulated, a diode may do the trick. If you'd rather err on the high-side (when the battery is new & fully charged) a Schottky diode will drop about 0.3V.
There are a couple of issues with regulators... The battery voltage is going to drop as the battery ages. You can look for a low dropout (LDO) regulator, but when the battery drops down near 2.5V, at some point the regulator will drop out of regulation.
There are boost-buck (switching) regulators that can either reduce or boost the voltage and they can be very efficient. But a low power, I don't think you'll get anywhere the rated efficiency and the battery will probably be drained quickly.
Any regulator circuit requires some power just to operate, so just hooking-up a regulator is going to drain the tiny battery to some extent.
hi!!!
First of all, thank you for your help.
You are right!
Well. Actually I'll run the Atmega328(@8Mhz) with this 2.5v.
I'm not sure If I can connect the 3.3 battery directly to the arduino.
My total current is about 8mA at peak . my project is a variometer that emites beeps(it may cause the voltage to drop if i don't use a regulator and Atmega may reset or something. Am I right)?
Or I can use a the 3v battery cell directly to the Atmega?
What do you think?
i am not quite sure, but on the data-sheet http://www.atmel.com/Images/Atmel-8271-8-bit-AVR-Microcontroller-ATmega48A-48PA-88A-88PA-168A-168PA-328-328P_datasheet_Summary.pdfyou can read that they all will work with a voltage between 2.7v and 5.5v...
so it should work!
hi!!
I think it will work, I'm just afraid about voltage dropout when the device beeps.. Maybe the unstable voltage may reset the atmega
Well. I'll try and then let you know!
tks!
To run at 2.5V you'll have to reprogram the brown-out-detector fuses to
either inhibit brown-out detection or change the threshold from 2.7V to
1.8V.
With this regulator you can run at zero volts drop:-
Step up / down buck boost regulator
You can run your Microprocessor just fine directly from the CR2450 cell. A 8 mA load will not sag the voltage deep enough to reset your MCU.
Give it a go!
// Per.