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Power Supply problem for SIM900

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SiddharthGajjar

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i am using GSM Module SIM900
i have design certain power suplly and regulator circuit using LM2596 adjustable with resisitor divider network. as it is open ciruit network i got 4.2 Volt DC but here problem arise that when i connect my modem with it the voltage across the modem drop down from 4.2 to 3.2 volt.
i find some circuit on internet using variable pot. but as i am designing a product so i don't want to use that.

i've also tried LM2576 but disappointed.

please give me the solution so that i can get 4.0 regulate voltage.

- - - Updated - - -

and LM2576 5.0 fixed voltage regulator
 

a resistive divider will not work. Instead
connect a 1n5401 (or 02) diode in series with the output of LM2576.
 
What is your input voltage range? I guess the input voltage is not sufficient enough to provide the output. That's the reason you are output voltage getting lower to 3.2V
 

Hi

Code: 
a resistive divider will not work.
For sure a voltage divider is the solution.

At LM2576 datasheet near figure 22 there is the formula how to calculate the resistors.
Simple math.
****
please give me the solution so that i can get 4.0 regulate voltage.
Click to expand...
Its all given in the datasheet. Read it carefully...maybe multiple times.

****
I agree with hobbyckts...

****
If you need help with your circuit, so show it to us. With values, part names... complete information.

Klaus
 
Provide the values of the resistors which you have used for the voltage divider circuit.
 

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