ISNS pin sets the over current protection level. OCP1 is peak current protection level; OCP2 and OCP3 are average current protection levels. The typical threshold voltages are 4.0 V, 0.6 V, and 0.43 V, respectively.
Set OCP3 level at 130% of full load. Thus, the sensed average input current level at full load is given by:
The current sense ratio can then be calculated:
Select a current sense capacitor first, since there are less high voltage capacitor choices than resistors:
Then calculate the required ISNS resistor value:
After the current sense ratio is determined, the peak ISNS pin voltage at full load can be calculated:
The peak resonant current at OCP1 level is given by:
The peak secondary-side current at OCP1 level is given by: