The inverting comparator with hysteresis requires a three-resistor network that is referenced to the comparator supply voltage (VCC), as shown in Figure 38. When VIN at the inverting input is less than VA, the output voltage is high (for simplicity, assume VO switches as high as VCC). The three network resistors can be represented as R1 || R3 in series with R2. Equation 1 defines the high-to-low trip voltage (VA1).
When VIN is greater than VA, the output voltage is low, very close to ground. In this case, the three network resistors can be presented as R2 || R3 in series with R1. Use Equation 2 to define the low to high trip voltage (VA2).
Equation 3 defines the total hysteresis provided by the network.