The TLV40x1 comparators have a Power-on-Reset (POR) circuit which provides system designers a known start-up condition for the output of the comparators. When the power supply (V_S) is ramping up or ramping down, the POR circuit will be active when V_S is below V_POR. For the TLV4021 and TLV4031, the POR circuit will force the output to High-Z, and for the TLV4041 and TLV4051, the POR circuit will hold the output low at (V-). When V_S is greater than, or equal to, the minimum recommended operating voltage, the comparator output reflects the state of the input (IN).

The following pictures represent how the TLV40x1 outputs respond for V_S rising and falling. For the comparators with open-drain outputs (TLV4021/4031), IN is connected to (V-) to highlight the transition from POR circuit control to standard comparator operation where the output reflects the input condition. Note how the output goes low when V_S reaches 1.45V. Likewise, for the comparators with push-pull outputs (TLV4041/4051), the input is connected to (V+). Note how the output goes high when V_S reaches 1.45V.

Figure 8-1 TLV4021/4031 Output for V_S Rising

Figure 8-3 TLV4041/4051 Output for V_S Rising

Figure 8-2 TLV4021/4031 Output for V_S Falling

Figure 8-4 TLV4041/4051 Output for V_S Falling