The LM73605-Q1/6-Q1 a built-in power-good (PGOOD) flag to indicate whether the output voltage is at an appropriate level or not. The PGOOD flag can be used for start-up sequencing of multiple rails. The PGOOD pin is an open-drain output that requires a pullup resistor to an appropriate logic voltage (any voltage below 15 V). The pin can sink 5 mA of current and maintain its specified logic low level. A typical pullup resistor value is 10 kΩ to 100 kΩ. When the FB voltage is higher than V_PGOOD-OV or lower than V_PGOOD-UV threshold, the PGOOD internal switch is turned on, and the PGOOD pin voltage is pulled low. When the FB is within the range, the PGOOD switch is turned off, and the pin is pulled up to the voltage connected to the pullup resistor. The PGOOD function also has a deglitch timer for about 140 µs for each transition. If it is desired to pull up PGOOD pin to a voltage higher than 15 V, a resistor divider can be used to divide the voltage down.

Figure 8-15 Divider for PGOOD Pullup Voltage

With a given pullup voltage V_PU, select a desired voltage on the PGOOD pin, V_PG. With a selected R_PGT, the R_PGB can be found by:

Equation 22.

When the device is disabled, the output voltage is low, and the PGOOD flag indicates logic low as long as V_IN > 2 V.