50V Drain Supply Voltage - LNK304
Comments
Hello Jorg,
thanks for sharing your experience - makes my role on the forum that much more enjoyable! Could you share your schematic? Depending on the configuration it may be possible to tell if the issue is power delivery (to charge the output caps within the auto-restart time as you correctly pointed out) or insufficient voltage to keep the LNK305 operating. If it is too low an input voltage you can monitor the BP pin voltage with a scope - but caution in needed depending if the SOURCE node is a switching node or not (hooking up the scope ground may cause a short). If the BP pin goes below 4.8 V during startup the device will stop switching until the voltage charges back to 5.8 V - this would indicate insufficient voltage to operate the IC. Again PI only guarantees operation to 50 V.
If you post your schematic I can check if that'll work.
Cheers
PI-Chekov
Hello Quintin,
PI can only guarantee the operation of the device over the full device temperature range at a drain voltage of 50 V minimum. This ensures that sufficient current is available to operate the IC (charging of the BP pin capacitor during the MOSFET off time).
You can extend the operating voltage range by supplying current to the BP pin externally. The following DI shows the principal.
http://www.powerint.com/sites/default/files/PDFFiles/di152.pdf
Hope that helps
Cheers
PI-Chekov