LED2001 no output

[Dsun.21]

Dear Support and Expert, 

We are using LED2001 to drive a LED, 2V@4A. the 6 boards come back. 4 work good but 2 no output voltage. we are using QFPN package, is there a way to check the pins are properly soldered beside take it out and reinstall? 2. is it possible that the components and layout make the driver working in a marginal area? in our case, the design seems working but not good. how to optimize the design from the schematic point of view? I will pay attention when we do the next layout.

Thank you,

David

[Dsun.21]

Here is the recommended design from eDesignSuite, the above is a working design copied from an old project. may be the minor layout variation or the cable length change caused the problem. I don't know where the original come from. if possible, could anyone tell me what are the factors that make the design worse than the eDesignSuite suggestion? 

Thank you,

David

[Dsun.21]

I copied the schematic from STEVAL-ILL054V2. I don't full understand the red circuit marked portion. could anyone explain this to me?

Thank you,

David