ATtiny3217 Curiosity Nano has a VBUS output pin that can be used to power external components that need a 5V supply. The VBUS output pin has a PTC fuse to protect the USB against short circuits. A side effect of the PTC fuse is a voltage drop on the VBUS output with higher current loads. The chart below shows the voltage versus the current load of the VBUS output.
Figure 1. VBUS Output Voltage vs.
Current