In my earlier post, I was using LM317 for SIM900 but due to some voltage drop problem, I decided to go with LM2576. I am trying to step down the voltage from 12v to 4.5v using LM2576. I have studied the voltage calculation formula described on page 21. For the time being, I am just testing it on breadboard so have not connected the capacitors and diode at the output. Following is the schematic
According to the voltage calculation formula:
O/P Volts = Vref(1 + R2/R1) O/P Volts = 1.23(1 + 4700/2000) O/P Volts = 1.23(1 + 2.35) O/P Volts = 4.12v
So the calculation shows output voltage of 4.12v but in practical it is showing 5.64v.
Is my calculation wrong or I am doing something wrong in the circuit. Please help.?