TIDUET3 Design guide

TIDUET3 February 2021

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2.4.2.11 Current Sense Circuit (ISNS Pin)

The ISNS pin sets the overcurrent protection level. OCP1 is peak current protection level; OCP2 and OCP3 are average current protection levels. The threshold voltages are 0.425 V, 0.56 V, and 4.03 V, respectively. Set the OCP3 level at 140% of full load. Thus, the sensed average input current level at full load is given by:

Equation 49.

The current sense ratio can then be calculated:

Equation 50.

Select a current-sense capacitor first because there are fewer high-voltage capacitor choices than resistors. C_ISNS = 330 pF Then calculate the required ISNS resistor value:

Equation 51.