I am working with the National Semiconductor LM3404 that is a buck regulator I am using to drive a single high power LED. I threw together a small PCB to test and make sure I have everything working. And to my surprise it works the first time I turn the power on.
Datasheet: **broken link removed**
Attached to this post are some quick pics to give you an idea of what I'm working with...I know its not much, and the board is kind of messy, but it gets the job done...
Ok now for the problem...After the board runs for a few minutes at its designed output of 750mA, the current through the LED drops suddenly to ~18mA...After letting it run at for a few moments longer it settled at about 16mA and I noticed that they recirculating diode is hot to the touch...I unplugged the power everything cooled down promptly...And upon applying power everything repeated...
This time I allowed the circuit to run continuously at ~16mA the diode never got any hotter than before...So in an effort to cool it off while still running I blew onto the board...the longer and harder I blew the higher the current would go...Up to about 25mA...No where near the designed 750mA...
The diode in question is the Schottky B130LAW: **broken link removed**
It is rated at 30V and 1A in the SOD-123 package...From the LM3404 datasheet this seems to be a suitable diode for use in this situation...Unfortunatly I have poor selection of diodes on hand, and ZERO schottky diodes laying around...
I'd appreciate any comments or previous experience on this topic...This board is being use just as a proof of concept, since I have never used this chip before...Eventually I'd like to incorporate it into a larger project, but not unless I can iron out this bugs...
Thanks for all your time, and help...
Datasheet: **broken link removed**
Attached to this post are some quick pics to give you an idea of what I'm working with...I know its not much, and the board is kind of messy, but it gets the job done...
Ok now for the problem...After the board runs for a few minutes at its designed output of 750mA, the current through the LED drops suddenly to ~18mA...After letting it run at for a few moments longer it settled at about 16mA and I noticed that they recirculating diode is hot to the touch...I unplugged the power everything cooled down promptly...And upon applying power everything repeated...
This time I allowed the circuit to run continuously at ~16mA the diode never got any hotter than before...So in an effort to cool it off while still running I blew onto the board...the longer and harder I blew the higher the current would go...Up to about 25mA...No where near the designed 750mA...
The diode in question is the Schottky B130LAW: **broken link removed**
It is rated at 30V and 1A in the SOD-123 package...From the LM3404 datasheet this seems to be a suitable diode for use in this situation...Unfortunatly I have poor selection of diodes on hand, and ZERO schottky diodes laying around...
I'd appreciate any comments or previous experience on this topic...This board is being use just as a proof of concept, since I have never used this chip before...Eventually I'd like to incorporate it into a larger project, but not unless I can iron out this bugs...
Thanks for all your time, and help...