7.3.6 Power Good

The power-good (PG) pin is an open-drain output and can be connected to a regulated supply through an external pullup resistor. The maximum pullup voltage is listed as V_PG in the Recommended Operating Conditions table. For the PG pin to have a valid output, the voltage on the IN pin must be greater than V_UVLO(RISING), as listed in the Electrical Characteristics table. When the V_OUT exceeds V_{IT(PG,RISING)}, the PG output is high impedance and the PG pin voltage pulls up to the connected regulated supply. When the regulated output falls below V_{IT(PG,FALLING)}, the open-drain output turns on and pulls the PG output low after a short deglitch time. If output voltage monitoring is not needed, the PG pin can be left floating or connected to ground.

By connecting a pullup resistor to an external supply, any downstream device can receive power-good (PG) as a logic signal that can be used for sequencing. Make sure that the external pullup supply voltage results in a valid logic signal for the receiving device.

The recommended maximum PG pin sink current (I_PG-SINK) and the leakage current into the PG pin (I_LKG(PG)) are listed in the Electrical Characteristics table.

The PG pullup voltage (V_{PG_PULLUP}), the desired minimum power-good output voltage (V_PG(MIN)), and I_LKG(PG) limit the maximum PG pin pullup resistor value (R_{PG_PULLUP}). V_{PG_PULLUP}, the PG pin low-level output voltage (V_OL(PG)), and I_PG-SINK limit the minimum R_{PG_PULLUP}. Maximum and minimum values for R_{PG_PULLUP} can be calculated from the following equations:

For example, if the PG pin is connected to a pullup resistor with a 3.3-V external supply, from Equation 2, R_{PG_PULLUP(MAX)} is 11 MΩ. From Equation 3, R_{PG_PULLUP(MIN)} is 5.8 kΩ.