When DI_EN goes low and PP is high, the DOI current sink is switched-off almost immediately. Now the output is tri-state until the part is ready for DO operation mode. It takes a while to set-up DO mode and during this time the output will float to ~1.2V, due to the tri-state leakage and load conditions. When DO mode starts to work, the output goes to ~0.5V due to PP operation, which drives the output to one diode above GND.
The offset in DI mode (i.e. ~0.75V) is the compliance voltage of the current sink.
To summarize you have 3 ON state states for DOI voltage with PP=1:
The offset in DI mode (i.e. ~0.75V) is the compliance voltage of the current sink.
To summarize you have 3 ON state states for DOI voltage with PP=1:
| DI_EN | IN | OUT | Description |
|---|---|---|---|
| 0 | 1 | VDD | HS ON, DOI to VDD |
| 0 | 0 | 0.5V | LS ON, DOI to GND through an internal diode |
| 1 | X | 0.75V | Current sink on DOI pulls down the node |
Then you have DOI to ~1.2V when in tri-state (e.g. HS/LS OFF due to start-up phase or due to a fault condition)