I have built the attached Buck SMPS and put a resistive load on the output to see if it could source close to the max rated output current of 2A.

The output voltage is 5.45V unloaded but starts to drop with a resistive load of 2k to 5.35V and pulling 27mA for some reason not 2.6mA.

Looking at the estimates, it says output power is 5V x 2A. So should the voltage hold at 5V up to 2A before it starts to decrease with more than 2A being pulled.

 

have you measured the resistor load, your figures would suggest a 200 ohms load?

 

Yes, measured the load. reads 2k and checked the bands Red, Black, Red, Red. Rechecked the voltage at 5.5V and current is 28mA. I realized I used a 2.2uF electrolytic cap for C6 in the error amplifier so changed that to 20 x 0.1uF ceramic caps in series with hasn't changed anything.

 

I have built the attached Buck SMPS and put a resistive load on the output to see if it could source close to the max rated output current of 2A.

The output voltage is 5.45V unloaded but starts to drop with a resistive load of 2k to 5.35V and pulling 27mA for some reason not 2.6mA.

Looking at the estimates, it says output power is 5V x 2A. So should the voltage hold at 5V up to 2A before it starts to decrease with more than 2A being pulled.

Yes.

If you build this on a white board, it will not work as advertized. It has to be on a PCB or at least hand-wired, soldered, using large, short conductors.

 

You are reading the resistor backwards. Red-Red-Black is 220 ohms.

ak