I'm npt at all sure just decoupling it would help - the main issue with it is that my notes explicitly state that the FB trace should be as short as possible, but in the layout shown it loops round the board. See the "Key points" bullet list at http://www.desmith.net/NMdS/Electronics/NixiePSU.html#design
You need to 'scope the FB pin - it should be very smooth - if you look at my top mask, you'll see that the trace to pin 3 is very short - http://www.desmith.net/NMdS/Electronics/NixiePSU/MAX%201771%20V5%20PCB%20top%20and%20bottom%20layers.png Can you show us the schematic of your PSU? The arrangement of the potential divider round the FB pin looks odd too, but its difficult to be sure from just the board layout. Nick On Jan 14, 12:14 am, marta_kson <[email protected]> wrote: > Your problem seems to be very common on the 1771. My experience is > that the feedback input is e x t r e a m l y sensitive to > interference. Try to decouple it to ground through a few hundred pF > and the problems might go away. I have not found the exact reason to > my own problems, but expect it's pulses injected to that input in some > way that changes the setpoint if the switcher is on or off. The data > sheet advices against a decoupling, but it seems to work. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
