LM5001-Q1: LM5001Q1

Hi Akanksha,

Thanks for your patience. Is there a reason why you chose this device and not a newer device like the LM51581-Q1?
Newer devices usually have better available design resources, like Quickstart Calculators.

The maximum SEPIC duty cycle is calculated according to Dmax = (Vout + Vf) / (Vin,min + Vout + Vf), with Vf being the forward voltage of the diode.
In your case, Dmax would be 0.784, assuming Vf=0.7V. While the worst case maximum duty cycle limit is given in the datasheet as being 80%.

As you know, the device has an integrated FET, thus limiting the flexibility for applications. 
Furthermore, in the "Designing A SEPIC Converter" - App Note, the rms current which will flow through the switch is calculated in section 4.
Assuming the peak-to-peak ripple current to be approximately 40% of the maximum input current at the minimum input voltage, the peak switch current would equal 1.28A, which violates the 1A current limit of the integrated MOSFET.

Thus you can't operate this device with these parameters.

Thank you and best regards,
Bryan