Using TL431/OPTO feedback with LNK304 based HV Buck

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Hi,
For HV Buck using LNK304 as on page 6 of datasheet (2nd schem down)...

LNK304 datasheet
http://www.mouser.com/ds/2/328/lnk30...306-179954.pdf

...Is their any reason that we cant use a TL431 and a divider with the opto instead of just a zener?
(we don’t want the zener’s poorer tolerance)

Hi,

You may opt to design with the TL431 instead of the zener diode, however it may have an effect in terms of the LinkSwitch-TN response. The LinkSwitch-TN utilizes on/off control; having a TL431 in your feedback circuit may cause unexpected behaviour of output voltage ripple, TL431 operation, and other performance criteria. You may want to read this forum discussion: ( https://ac-dc.power.com/forum/low-power-design/tl431-vs-zener/ )for a better idea. If you have time in your design schedule, you may want to compare which feedback circuit would achieve better efficiency, ripple, EMI and other performance criteria to best meet specifications.

Regards,