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:

Equation 50.

The current sense ratio can then be calculated:

Equation 51.

Select a current sense capacitor first, since there are less high voltage capacitor choices than resistors:

Equation 52.

Then calculate the required ISNS resistor value:

Equation 53.

After the current sense ratio is determined, the peak ISNS pin voltage at full load can be calculated:

Equation 54.

The peak resonant current at OCP1 level is given by:

Equation 55.

The peak secondary-side current at OCP1 level is given by:

Equation 56.