The +5V system power is from the USB interface.
Only the ultrasonic transceiver is supplied directly by the +5V, namely the VDD. All other circuits in the system are supplied by 3.3V, named V_MCU from an LDO.
Figure 1. Power Supply for the
System
As shown in the image above, R109 and C109 can be mounted to enhance the ESD protection performance.
Note: Parts marked with "N.M" should not be
mounted by default.