Hi,
I built a isolated DC/DC converter with the TPS55010 . For EMC reasons the converter uses a switching frequency of 1MHz. However I have now the problem, that occasionally the TPS55010 burns down. (With no or only very light load connected) The failure mechanism is a short of the PH pin to GND. Probably this is by a short in the low side switching FET or an destroyed protection diode.
Most probably (I have to check this when I am back in the lab) the destruction happens during switching off the regulator. (However – it could also happen right after switching on). However I notice that the regulator is working, switch it off and on again and it is gone.
I have attached the schematic. In between I have added 5.6V Z-Diodes to the input supply and output supply to generate a light load at the secondary side and to protect the TPS55010 primary. It did not help – which is not so surprising because the low side switch died – not a high side/VCC related part.
Is it possible that the capacitor C1015 (which is actually a 10uF type to get the 4.7uF at the expected voltage) is too large and generates a large reverse current during power down thru the protection diodes in the chip (and therefore destroying them like an antifuse)?
Thank you,
Martin Laabs
