How to use the buck switching regulator ST1S03PUR, and dimension the components value for an out 3v3 and 500mA?

[LUruc.1]

Hi, latelly I am trying to use the buck switching regulator ST1S03PUR and I have some problems with it. It should be something easy to do but seems like not.

I have a DC Vin 12V and i want as out 3V3 and 500mA.

For the Vout I am using the formula from datasheet VO = VFB [1 + R1 / R2].

Vfb=0,8V.

I'm a litle confused because I am following the datasheet and it is easy to put out 3v3 but once I put a load ST1S03PUR can not hold it and breaks puting in S.C Vin and GND.

Vin 12V from an lnk3206 ac/dc switching 300mA out.

For sure I'am doing something wrong and one of them is the layout of the pcb but for sure even the layout isn't the best I could do , I should not have this kind of problem.

No temperature problems detected.

Could you help me to understand what's wrong in my case?

Thank you

Leonard

[Muhammed Güler]

I have worked with ST1S14PHR before. could not start directly on load. It was working if I connect the load with 1-2 second delay.

[LUruc.1]

Hi, yes I tried also this way but no change, anyway if this is valid also for ST1S03PUR than maybe it is the case to find diferent solution for my applacation.

Thank you

[Peter BENSCH]

You can do so much wrong with the layout of a buck regulator that the circuit does not work at all.

Are you able to share the layout of your design?

Regards

/Peter

[LUruc.1]

Hi Peter,

I don't have it now anyway I already order the evaluation board and and make some test.

Thank you

Leonard