The LM5146 provides a PGOOD flag pin to indicate when the output voltage is within a regulation window. Use the PGOOD signal as shown in Figure 8-4 for start-up sequencing of downstream converters, fault protection, and output monitoring. PGOOD is an open-drain output that requires a pullup resistor to a DC supply not greater than 13 V. The typical range of pullup resistance is 10 kΩ to 100 kΩ. If necessary, use a resistor divider to decrease the voltage from a higher voltage pullup rail.

When the FB voltage exceeds 94% of the internal reference V_REF, the internal PGOOD switch turns off and PGOOD can be pulled high by the external pullup. If the FB voltage falls below 92% of V_REF, the internal PGOOD switch turns on, and PGOOD is pulled low to indicate that the output voltage is out of regulation. Similarly, when the FB voltage exceeds 108% of V_REF, the internal PGOOD switch turns on, pulling PGOOD low. If the FB voltage subsequently falls below 105% of V_REF, the PGOOD switch is turned off and PGOOD is pulled high. PGOOD has a built-in deglitch delay of 25 µs.