Problem with LM22677

Can you post the schematic that you used along with a picture of the layout.  This should help me try to figure out what is going wrong.

Thanks,

Marc

Hallo Marc

Thank you for your answer.

That is my schematic with LM22677

thanks for your Help

Youssef

Hi Youssef,

Thank you for the schematic.  I see the problem now.  The max voltage on the Enable pin is 6V.  You need to add a resistor from Enable to ground in the range of 50K.  This will create a voltage divider from Vin to lower the maximum voltage seen by the pin, but still allow the part to turn on when Vin rises.

Regards,

Marc

hi Marc,

thanks for your answer.

I've done it before in my circuit, but I had the same problem.
I have now done 50k, I get the same problem.
I turn off the power, then on again, then breaks lm22677,why.....

that is my old circuit

OK Next step.

Try removing D2 and L2 and replace them with a short. 

Your feedback resistors are tied after this filtering, and this may be causing instability in your design.  The inductor adds an additional pole which might be affedting stability.  Let me know what happens.

Marc

hi Marc,

thanks for your answer.

D2 and L2 I have removed, but I get the same problem when switching on and off
I built D2 as protection for lm22677
can you suggest me what, why do I get the same problem.

How quickly are you cycling the EN when you see the failure?

Please supply waveforms of the switch pin, vout, and vin when you cycle EN.

Be sure that the EP is soldered down to the ground plane.

I would suggest starting with a simple EVM circuit first and make sure that works.  Then add

the extra components you need for your application until you discover the problem.

Frank D

hallo Frank,

thanks for your answer

I have everything you've given me suggested.
when ENABLE pin I made, that the regulator has to work from 21v.
but the problem now, when I do a load, then will break even with 500mA.

I can understand that, not normal as Iout 5A, what did I do wrong

Youssef