LNK6766K - Voltage Range Settings

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I am using the LNK6766K in a flyback design.  Have had a couple issues.

1.  I am using an OEM transformer with relatively low primary inductance.  The part was dropping into the 3-5mS dead time causing my supplies to be unstable.  Increased the cap on teh feedback pin which resolved this, but may be leading to a secondary problem...

2.  My voltage limits are not working as calculated.  Been awhile since originally designed, but believe the top resistor in the feedback path sets the input voltage range.  I designed this to run from 30-100V, but the system does not start up at 72V (works fine at 48V.)  My top feedback R = 22K.

Questions:

1. Is there something else I should be doing to fix item 1?  The cap on the feedback line is now 100pF; was originally 18pF.  

2.  What other factors determine the voltage thresholds?  As per the data sheet I thought I had this...

 

Hi,

Could you please share your schematic and PIExpert/PIxls design file?

Regards,

PI-NANO