Some applications monitor rails other than the one that is powering the comparator. In these applications the resistor divider used to set the desired threshold is connected to the rail that is being monitored.

Figure 9-2 Monitoring a Voltage Other than the Supply

The TLV40x1Ry can monitor a voltage greater than the maximum (V+) with the use of an external resistor divider network. Likewise, the TLV40x1 can monitor voltages as low as the internal reference voltage (0.2 V, 0.5 V, or 1.2 V). The TLV40x1Ry also has the advantage of being able to monitor high impedance sources since the input bias current of the input (IN) is low. This provides an advantage over voltage supervisors that can only monitor the voltage rail that is powering them. Supervisors configured in this fashion have limitations in source impedance and minimum sensing voltage.