Figure 11-1 illustrates an example of how to adjust the voltage threshold with external resistor dividers. The resistors can be calculated depending on the desired voltage threshold and device part number. TI recommends using the adjustable (0.8V voltage threshold device) when setting adjustable voltage thresholds. This variant bypasses the internal resistor ladder.

For example, consider a 12V rail, V_MON, being monitored for overvoltage (OV) using of the TPS3762D02OVDDFRQ1 variant, as shown in Figure 11-1. The monitored OV threshold, denoted as V_MON+, is the desired voltage where the device asserts the reset. For this example V_MON+ = 35V. To assert an overvoltage reset the voltage at the sense pin, V_SENSE, needs to be equal to the input threshold positive, V_ITP. For this example variant V_SENSE = V_ITP = 0.8V. Using R₁ and R₂ the correlation between V_MON+ and V_SENSE can be seen in Equation 8. Assuming R₂ = 10kΩ, and R₁ can be calculated as R₁ = 427.5kΩ.

The TPS3762D02OVDDFRQ1 comes with variant specific 2%, 5%, or 10% voltage threshold hysteresis. For the reset signal to become deasserted, V_MON must go below V_ITP - V_HYS. For this example variant a 2% voltage threshold hysteresis was selected. Therefore, V_MON equals 34.3V when the reset signal becomes deasserted.

There are inaccuracies that must be taken into consideration while adjusting voltage thresholds. Aside from the tolerance of the resistor divider, there is the internal resistance of the SENSE pin that can affect the accuracy of the resistor divider. Although expected to be very high impedance, users are recommended to calculate the values for the design specifications. The internal SENSE resistance (R_SENSE) can be calculated by the SENSE voltage (V_SENSE) divided by the SENSE current (I_SENSE) as shown in Equation 9. V_SENSE can be calculated using Equation 7 depending on the resistor divider and monitored voltage. I_SENSE can be calculated using Equation 8.