I need a 9A constant current source using a buck regulator to drop 7 volts to around 3.6v for the SST-90 LED. Any IC recommendations?

My previous answer seems to be swallowed up by the interwebs, so I'll try again :) I prefer to use Linear components for these kind of applications instead of National. This is partly a question of personal taste, but I also like to have a decent simulator available (Lt-spice) and not that crappy webbench abomination. And in switching regulator design, simulation is a must imho to verify your circuit.

The current that you need is not a problem, but you will probably need discrete components (coil, diode, transistor) in your regulator instead of a monolithic regulator IC. Take a look at LT3755.

A few considerations here: the LM3409 datasheet suggests that 5A is a typical application, so 9A might be pushing it a bit. The Vin_min for this device is 6V. If your power source is a battery with nominal voltage of 7V, it will not last very long before the Vin_min is exceeded.

There is no need to use the HV variant unless you plan on hooking this up directly to an automobile power supply while cranking, and even then, the regular part would probably be ok. At that current level, National seems to have a better selection of parts if you can get your voltage input to 12 volts (8 D-cells? ), which would allow you to pick parts with Vin_min of 9V.

I'm building a dive light, based on the P90 led, and thus have the same problem coming from a 12V source, trying to feed a 4V led with 9A of current. This led does look promising (LT3743 ), however I'm afraid the total circuit will become big, perhaps too big to build in a flashlight... Still looking for an easier solution... Let us know when you find a working solution!

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.