PPD is a multifunction pin that has two voltage thresholds, PPD1 and PPD2.
PPD1 permits power to come from an external low voltage adapter, that is, 24 V, connected from VDD to VSS by overriding the normal hotswap UVLO. Voltage on PPD more than 1.55 V (VPPDEN) enables the hotswap MOSFET, inhibits class current, and enables T2P. A resistor divider per Figure 34 provides ESD protection, leakage discharge for the adapter ORing diode, reverse adapter protection, and input voltage qualification. Voltage qualification assures the adapter output voltage is high enough that it can support the PD before it begins to draw current.
PPD2 enables normal class regulator operation when VPPD is more than 8.3 V to permit type 2 classification when APD is used in conjunction with diode DVDD (see Figure 33). Tie PPD to VDD when PPD2 operation is desired.
The PPD pin has a 5-μA internal pulldown current.
Locate the PPD pulldown resistor adjacent to the pin when used.
PPD may be tied to VSS or left open when not used.