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Powering GSM module from 5V

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gauravkothari23

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Hi all..
i am trying to make a project using GSM Module and 89S52 microcontroller to send messages.
MCU works on 5V, but my GSM module works only on 3.3V - 4.2V (4.0 recommend by datasheet). How can i convert 5V to get 4V to power my GSM module.
My MCU consumes hardly 100 to 150 mA of current but for GSM module i need atlest 2.2 Amps of current.
can i use two diodes in series to drop near about 1V
I am using Small SMPS where i get output of DC 5V 3-Amps to power my circuit.
 

For the power side of things, you can use a LDO 5v to 3v3 regulator.
You will also need to consider the data lines between the two devices.
The 'correct' way is to use a 'level converter' (also called a level shifter) IC - Google searches show lots of options.
For the signals going from 3v3 to 5v only, you can use a transistor. Going the other way only you can use a suitable resistor divider.
Also I'd look at other members of the same MCU family that operate on 3v3 and save yourself a whole lot of interfacing issues.
Susan
 

powering the GSM module with 3.3V is not reliable because as per the datasheet 4V is recommended.
i have even tried using 3.3V, but the things are not working perfectly. so i need to power it by 4V.
can i use a voltage divider as image attached.
 

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Hi,

I think I wouldn't use a voltage divider, because when I think of the voltage drop across R4 with 2.2A... a hard circle to square. That's only one reason, another is temperature, self-heating, etc.

I'd use an adjustable 5A LDO, it only needs a couple of capacitors and a couple of resistors, a minimum load (maybe 5 to 10 mA) - like an indicator LED to show the 4V line is powered, and the voltage will be reliable.
 

You can use LM257-5.0. It needs only 3 external components and provides 5V 3A output and SIM900 only needs 2.5A burst current for 200 milli seconds while sending SMS.
 

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