LM5166: Turn off and doesn't come back without powercycle

HI

can you share the schematic? and do you have detailed 'shutdown' waveform?

Thanks

Circuit is as follows, unfortunately I have not been able to capture waveforms yet at the moment the convertor shuts down.

HI

below is my idea:

in PFM mode, the max output capability is 500mA, if the second stage draw output high than 500mA, it will make 12V drop down, cause secondary work at constant power(for example 5V 1A) , so Vin dereasing will make current larger which make the current more larger so it will drop down to TPS561201 VIN UVLO then try to restart but it can't .

this is my assumption, but if this isn't match the issue, you may need take look at the shutdown waveform with SW see what caused the issue.

Thanks

Hi Daniel

Thank you for that, however I do not believe this is the problem.

In the shut down condition no current is being drawn from the 48V input supply.  It drops from normal 8 to 12mA  down to 0mA. It is as if EN is < 0.6V (ie a hard shutdown) but EN is at almost 7V.

Craig