The overvoltage protection is set by configuring the R_{BOT_OVP} and R_{TOP_OVP} resistors. The overvoltage protection feature turns off the switch if the input voltage exceeds a predetermined value as described in Section 9.3.1. For this design, the goal is to have the overvoltage protection activate at a nominal voltage of 13.5 V. First set R_{TOP_OVP} = 100 kΩ with a 0.1% tolerance resistor, then use Equation 10 to calculate the nominal value of R_{BOT_OVP}. A nominal 9.31-kΩ 0.1% tolerance resistor best satisfies the equation.

Equation 10.

where

• V_OVPR(TYP) = 1.15 V
• R_{TOP_OVP} = 100 kΩ
• VIN_{OVP_RISE} = 13.5 V

In order to ensure the selected R_{BOT_OVP} value is acceptable for both the minimum and maximum OVP rising threshold, use Equation 11. VIN_{OVP_RISE(MIN)} is selected as the highest possible value that VIN will reach during nominal operation (to prevent false OVP trips). VIN_{OVP_RISE(MAX)} may be selected by the user as long as it is within the VIN of the Recommended Operating Conditions. These selections result in an allowable value of R_{BOT_OVP} between 9.214 kΩ and 9.650 kΩ. The selected 9.31-kΩ 0.1% tolerance resistor satisfies these constraints, even when taking into account its tolerance.

Equation 11.

where

• V_OVPR(MAX) = 1.18 V
• R_{TOP_OVP} = 100 kΩ
• R_tolerance = 0.01% = 0.001
• VIN_{OVP_RISE(MAX)} = 14 V
• V_OVPR(MIN) = 1.11 V
• VIN_{OVP_RISE(MIN)} = VIN × (1 + tolerance) = 12.6 V

Since the OVP pin has hysteresis, the OVP falling threshold will be different than the rising threshold. Therefore, in order to ensure the selected R_{BOT_OVP} value is acceptable for the OVP falling threshold, use Equation 12. VIN_{OVP_FALL(MIN)} and VIN_{OVP_FALL(MAX)} values may be selected using the same method as for VIN_{OVP_RISE(MIN)} and VIN_{OVP_RISE(MAX)}. These selections results in an allowable R_{BOT_OVP} value between of 9.129 kΩ and 9.460 kΩ. The selected 9.31-kΩ 0.1% tolerance resistor also satisfies these constraints, even when taking into account its tolerance.

Equation 12.

where

• V_OVPF(MAX) = 1.17 V
• R_{TOP_OVP} = 100 kΩ
• R_tolerance = 0.001
• VIN_{OVP_FALL(MAX)} = 14 V
• V_OVPF(MIN) = 1.09 V
• VIN_{OVP_FALL(MIN)} = VIN × (1 + tolerance) = 12.6 V

To summarize, using Equation 3 and Equation 4 with R_{TOP_OVP} = 100 kΩ and R_{BOT_OVP} = 9.31 kΩ, the eFuse will nominally go into overvoltage protection mode at 13.50 V and exit at 13.38 V. Taking into account the minimum and maximum OVP pin threshold and resistor tolerances, the switch will enter over voltage protection mode between 13.01 V and 13.88 V and exit between 12.77 V and 13.76 V.