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LM2576 ADJ buck converter

Thread starter #1
hello, i m trying to power my sim800 from a 12v dc supply, as sim800 work in 3.4-4.4v. i m using LM2576 ADJ to step down 12v to 4.2v. i have calculated value of resistor using a online calculator https://www.changpuak.ch/electronics/FeedbackCalculator.php , R1=8.2k & R2=3.3k. when i am using it on hardware its giving 5.16v instead of 4.2v. i have not connected any capacitor or diode as i just want to check voltage. Please suggest any simulation or provide proteus library for lm2576 as i am unable to find it.
 

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Thread starter #3

ChrisP58

Well-Known Member
#7
Yes. The output voltage is set by the ratio of the two feedback resistors, factoring in the internal reference voltage. See the datasheet for the exact equation, or use TI's WEBENCH® Designer.

But you must have ALL of the components needed for the complete circuit.
 

dr pepper

Well-Known Member
Most Helpful Member
#9
The sim circuit has a load resistor, dd you have a load resistor on the practical circuit, if not thats probably why its on the high side.
 

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