The TPS7A7100 has a power-good function that works with the PG output pin. When the output voltage undershoots the threshold voltage V_IT(PG) during normal operation, the PG open-drain output turns from a high-impedance state to a low-impedance state. When the output voltage exceeds the V_IT(PG) threshold by an amount greater than the PG hysteresis, V_hys(PG), the PG open-drain output turns from a low-impedance state to high-impedance state. By connecting a pullup resistor (usually between the OUT and PG pins), any downstream device can receive an active-high enable logic signal.

When setting the output voltage to less than 1.8 V and using a pullup resistor between OUT and PG pins, depending on the downstream device specifications, the downstream device can possibly be unable to accept the PG output as a valid high-level logic voltage. In such cases, place a pullup resistor between the IN and PG pins, not between the OUT and PG pins.

Figure 5-18 illustrates the open-drain output drive capability. The on-resistance of the open-drain transistor is calculated using Figure 5-18, and is approximately 200 Ω. Any pullup resistor greater than 10 kΩ works fine for this purpose.