Undervoltage detection is frequently required in low-power, always-on systems to alert the downstream device that a battery or supply voltage has drooped below the nominal voltage level. The TLV185x and TLV186x devices have an over-the-rail capability which allows the comparator to monitor high voltages up to 40V on the inputs while operating at lower supply voltages such as 3.3V, as shown in Figure 7-9. The high voltage battery V_BAT is divided down to be compared against a reference voltage, which can be set by a shunt regulator such as the TL431. When the voltage on the non-inverting input drops below the reference voltage, then the output of the comparator will toggle and send an alert signal to a MCU.

Figure 7-9 Undervoltage Detection