I am looking at the datasheet for the OSRAM Golden DRAGON® Plus LUW W5AM, a high power white LED.
It has a forward current of 20-1000 mA, surge current up to 2500 mA, and I think they want you to run it at 350 mA; that is what they use for most of the tests.
Notice that I emphasized the lower range of 20 mA. The forward current can not go below 20 mA. That is curious, but taken in isolation I would never have given it much thought.
Now, page 15 has a curious graph, titled Maximum Permissible Forward Current:
Here they iterate the minimum 20 mA operating current, even going so far as to exclude the area from the graph (it is covered with a grey block), and they use the strong words "Do not use below 20 mA".
Why can I not operate my LED at a current less than 20 mA?
Presumably they feel so strong about this that they have to warn me against it. Are there any electrical reasons, perhaps related to long-term reliability? Or is it just that they want me to use a more suitable LED?
I've tried to contact OSRAM about this, to no avail. Maybe it's not important to reply unless the customer is interested in a 100k purchase.