LNK306 random shutdown
We have been using the LNK306 as a flyback controler for ~3 years and are going into volume production. We started to see ~3% of our units go into a random shutdown condition for 3.5ms. I have not been able to determin a condition that would account for the 3.5ms time. We are driving 4 taps off a transformer controlled by a 6.8V tap, then using linear regulators to give controled 3.3V off of the 6.8V.
Attached is the switching waveform and a 3.3V signal used to triger at failure.
Comments
Our design is almost exactly following the example. The spacing from the opto is within an inch and the cap is right on the BP pins. Can feedback noise cause something like this? Is there anyone that I can speak with on the phone or direct email? Is there a process to return some of these parts that are showing the issue to have them analyzed ?
I will send you a private message
Hi
It is hard to determine the issue with a single scope image.
How is your layout? Do you have the BP pin capacitor (100nF) directly between the BP pin and a source pin?
What kind of feedback circuit are you using? How is the layout in that section of the circuit?
Here you can see the example of a feedback loop that works very well of the LNK-TN.