Pin Driver Strength

Figure 1. ATmega168PB: I/O Pin Output Voltage vs. Sink Current (VCC = 3V)
Figure 2. ATmega168PB: I/O Pin Output Voltage vs. Sink Current (VCC = 5V)
Figure 3. ATmega168PB: I/O Pin Output Voltage vs. Source Current (VCC = 3V)
Figure 4. ATmega168PB I/O Pin Output Voltage vs. Source Current (VCC = 5V)