8.3.7 Power Good (PGOOD)

The power-good version of LMR23630-Q1 has a built-in power-good flag shown on PGOOD pin to indicate whether the output voltage is within its regulation level. The PGOOD signal can be used for start-up sequencing of multiple rails or fault protection. The PGOOD pin is an open-drain output that requires a pullup resistor to an appropriate DC voltage. Voltage detected by the PGOOD pin must never exceed 15 V, and the maximum current into this pin must be limited to 1 mA. A typical range of pullup resistor value is 10 kΩ to 100 kΩ.

When the FB voltage is within the power-good band, +6% above and –6% below the internal reference voltage V_REF typically, the PGOOD switch is turned off, and the PGOOD voltage is as high as the pulled-up voltage. When the FB voltage is outside of the tolerance band, +7% above or –7% below V_REF typically, the PGOOD switch is turned on, and the PGOOD pin voltage is pulled low to indicate power bad. A glitch filter prevents false-flag operation for short excursions in the output voltage, such as during line and load transients. The values for the various filter and delay times can be found in the Timing Characteristics table. Power-good operation can best be understood by reference to Figure 21.

Figure 21. Power-Good Flag