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LM3463EVM: LED turn on voltage

Jose Araujo1
Prodigy 195 points
Part Number: LM3463EVM
Other Parts Discussed in Thread: LM3463

Hi everyone,

I was having a look at the documentation related to the evaluation board for the LM3463 (snva642a) when I came accross the formulas and data regarding the LED turn on voltage. The LED turn on voltage should be 5V higher than the VLED_Max_Cold (Vdhc_ready = Vled_max_cold +5V). I have also seen another relation between the turn on voltage and the resistances on the feedback node of the power supply, given by Vdhc_ready = 2.5V +(Rfb1 + Rfb2)/Rfb2 . So far so good but on page 5 of the document there's a practical example in which Rfb1 and Rfb2 are 39.8k and 3.9k respectively, for a LED turn on voltage (Vrail) of 48V. 

The problem is that if you solve the formula for the Vdhc_ready = 2.5V +(Rfb1 + Rfb2)/Rfb2 and change the resistances variables with its given value we get a Vdhc_ready of 28V, far bellow the 48V needed.  Is there something I am missing here? 

Thanks a lot in advance for your time.

Best regards,