Pin Driver Strength

Figure 1. I/O Pin Output Voltage vs. Source Current (VCC = 5V)
Figure 2. I/O Pin Output Voltage vs. Source Current (VCC = 3V)
Figure 3. I/O Pin Output Voltage vs. Sink Current (VCC = 5V)
Figure 4. I/O Pin Output Voltage vs. Sink Current (VCC = 3V)