Hi,
I have an L5973D set up for 28.5V output from 30V ish input for 2A current. The design requires the regulator to go to 100% duty cycle when the input voltage drops. At low currents (up to 1.5A) the device behaves correctly and smoothly transitions to 100% duty cycle as the input voltage drops. When the current is above 1.8A and the input voltage drop below 29.5V it completely drops the output voltage, maintains the current and is switching at 100KHz rather than the normal 250KHz. It's like it's gone into the short circuit protection mode. It can only be recovered by removing the load. Is this correct behaviour?
The design is good for 2.2A, I can't see that with the inductor I have that it is reaching the internal current limit of 2.5A min and I think it should be cycle by cycle limiting in this case and just lower output voltage a little not completely crash it.
Anyone have experience of this devices?
Thanks
Julian
