Hello,

We are designing ac to dc converter using hyper PFS and LCS family.

But there is Doubt in the datasheet while selecting R(start) and R(Fmin) Using the Equation Of R(FB).

According to datasheet R(start) is 10% lower than pull up resistor on DT/BF pin.

For our Design Application Fmax = 540Khz and Pull up Resistor is 11.6Kohm and from this R(start) will be 10Kohm (Approx- 10% lowe of Pull up on DT/BF). While i calculate R(FB) using the equation shown in the datasheet it gives the value 10kohm(Approx) and using R(FB)=R(start)+R(fmin), R(fmin)= 0 ohm(Nearer) but in the all example it shows nearer 35kohm to 40Kohm.

So, how i can select R(start) and R(fmin)? Alos there is not specified any calculation for Selecting R(opto) in datasheet. so, what should be it's value?

Waiting your Prompt Reply.

Thanks