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I need help with powering a microcontroller

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skakz

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pwering microcontroller

hi i am building a device with a 3.7 battery source and my microntroller needs max of 100mA and 3.6 V best voltage in 3.3

it needs 40 mA in normal mode and 60μA in powerdown mode

My major problem is to get 3.6 from 3.7 i will put a resistance and i get it;s value from V=IR which I do i use ?

if i used the 100mA and the microcontroller the R is 1Ω it's ok but if the current was less the voltage on the pin will be high

if i used 60μA then when the micrcontroller needs 40mA the voltage on the pin will be less than 3 !!

please some help me
 

pwering microcontroller

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Re: pwering microcontroller

Instead of a resistor use Schottky Barrier Diode with Vf≈0.35V ..
For example,
BAT15 has Vf=0.32V @ 10mA ..

Regards,
IanP
 

Re: pwering microcontroller

Instead of a resistor use zenner diode 3.6V
 

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    skakz

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pwering microcontroller

Zener can be good choice.....but I think you can feed 3.7V direclty to your uC, it should tolerate it!! Check the specs in the datasheet, I'm pretty sure it should work out.

Good luck
 

Re: pwering microcontroller

IanP said:
Instead of a resistor use Schottky Barrier Diode with Vf≈0.35V ..
For example,
BAT15 has Vf=0.32V @ 10mA ..

Regards,
IanP
Click to expand...

what is schottky barrier diode

Added after 4 minutes:

the zinner diode will help in case of the the voltage increases but will help in the other case

or
the zinner will provide V of 3.6 what ever the current is

Added after 1 minutes:

Jack// ani said:
Zener can be good choice.....but I think you can feed 3.7V direclty to your uC, it should tolerate it!! Check the specs in the datasheet, I'm pretty sure it should work out.

Good luck
Click to expand...



it works from 3 to 3.6
 

Re: pwering microcontroller

what is schottky barrier diode
Click to expand...
A shottky barrier diode is just one type of diode. Its advantage in this case is its low forward voltage drop. In order to use as IanP suggested, you have to put it in series with your battery. I think this option is better than using a zener diode.

Make sure that the voltage of the battery you intend to use doesn't go down with it state of charge. Lithium-ion batteries are a good choice, their voltage stays constant until their end-of-life.

You can also use a low-dropout regulator...

I also suggest that you don't try to use 3.7V directly, usually 3.6V is the absolute maximum rating!
 

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