L6591 issue

[VSimo.18]

Hi at everyone,

I designed a open loop dc/ac converter, but I met a big problem. The high side output did'nt work correctly over the 40V of Vhv. Over that value the output goes out derivates and the resistance from pin 14 and pin 13 is 5ohm. Aflter a few minutes the value return a nominal value.

At the first time I thought the a chip broken, but I changed it two times with the same behavior.

Someone had problems of this kind?

Thanks in advanced

Valter