The 6A4 diode is a general purpose diode for 60hz operations. It is not made to run at 300khz. What happened to the SB540 in your schematic?
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No. I now think the inductors are OK.Hi ronsimpson,
As you suggested me before Should i change the inductors???
Spice models are not very good. Little details are not in the models. I think the real parts equal models when SS is 0 to 2.0 volts. The real parts have a clamp at 2.4V so the voltage is limited to 2.4V. This clamp is not in the model. This is not a big problem.I have observed in LT spice that at soft start pin there is around 23V..but on my PCB am getting 2.4V..Can anyone knows about it??
Here are the files.
I'm thinking the problem is now with the input supply.
Samson, If you go into spice and change the spice analysis menu to start external supplies at 0 volts soft start will work and the 8 amp problem goes away.
I have observed in LT spice that at soft start pin there is around 23V..but on my PCB am getting 2.4V..Can anyone knows about it??
That is caused because you haven't changed the Spice analysis command to "start external supplies at 0 volts".
I have one more theory then I think you must take the measurements Ron S. has asked for.
Here is the theory: The .01 ohm sense resistor is very small. The traces on your PCB could easily be .05 ohms. So check this:
The resistor going to the sense pin should be connected at the top of the .01 ohm resistor. When I say at the top I mean right to it not an inch or cm away.
The other end of the .01 ohm resistor should have a big short trace (or wire) directly to the ground of the IC.
I have one more theory then I think you must take the measurements Ron S. has asked for.
Here is the theory: The .01 ohm sense resistor is very small. The traces on your PCB could easily be .05 ohms. So check this:
The resistor going to the sense pin should be connected at the top of the .01 ohm resistor. When I say at the top I mean right to it not an inch or cm away.
The other end of the .01 ohm resistor should have a big short trace (or wire) directly to the ground of the IC.
We need to see the PCB layout!