Configure the circuit as shown in Figure 8-3. Connect V+ to a 3.3 V power rail and connect V- to ground. The resistor network is used to create an early warning detection signal at OUT2, which will give a warning alert as V_MON approaches the max limit, changing state from a logic low to a logic high. OUT2 will stay high for a longer period until V_MON is no longer in the warning zone. OUT1 will be used when V_MON reaches the max limit and transition from a logic low to a logic high. This type of topology can be used for sensitive systems where advanced notice of the power supply over-voltage detection is needed.

Use V_MON2, the threshold for a low to high transition at OUT2, I_{IN_RES}, the current flow through the resistor network, to determine the minimum total resistance necessary to achieve the current consumption specification.

Equation 5.

where

• V_MON2 is the target voltage at which OUT2 goes high when V_MON rises
• I_{IN_RES} is the current flowing through the resistor network

After R_TOTAL is determined, R3 can be calculated using Equation 6. Select the nearest 1% resistor value for R3. In this case, 845 kΩ is the closest value.

Equation 6.

Use the voltage divider equation Equation 7 The voltage divider equation controls the V _MON1 voltage at which OUT1 will transition from a logic high to a logic low.

Equation 7.

where

• V_MON1 is the target voltage at which OUT1 goes low when V_MON falls

Rearranging Equation 7 to solve for R2 yields Equation 8 Select the nearest 1% resistor value for R2. In this case, 55.6kΩ is the closest value.

Equation 8.

Use Equation 9 to calculate R1. Select the nearest 1% resistor value for R1. In this case, 1.87 MΩ is a 1% resistor.

Equation 9.