3.6 Power Supply

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 3-10. 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.