The TPS53355 has power-good output that indicates high when switcher output is within the target. The power-good function is activated after soft-start has finished. If the output voltage becomes within +10% and –5% of the target value, internal comparators detect power-good state and the power-good signal becomes high after a 1-ms internal delay. If the output voltage goes outside of +15% or –10% of the target value, the power-good signal becomes low after two microsecond (2-μs) internal delay. The power-good output is an open drain output and must be pulled up externally.

The power-good MOSFET is powered through the VDD pin. V_VDD must be >1 V in order to have a valid power-good logic. It is recommended to pull PGOOD up to VREG (or a voltage divided from VREG) so that the power-good logic is still valid even without VDD supply.