I am designing an industrial LED light that is remotely controlled. It has a small micro which has a separate bleeder power supply and needs to be able to shut down the LED output. There's an additional need to keep the LNK454 from switching at all if possible, to reduce power line noise.
I have used a MOSFET power switch in series with the LNK power, but that's brute force and adds heat in the switch control circuit. I'd like to pull the FB voltage up above 2V instead. So my questions are:
1) What is the purpose of the 2uA bias at the FB pin? Does this ensure the LNK stays off if FB becomes disconnected?
2) What is the input impedance of FB? The app notes show 1k series resistors and 10nF. I'd need to raise that to at least 10k and 1nF in order to add an additional switchable pull-up (above 2V) to turn the LNK off.
I can easily disconnect the LED output string, but then the LNK's auto restart still makes noise on the AC line, and I'd like to avoid that.
Do you have other suggestions?
Is there a different part I should consider? - I don't need dimming ability.