In the CP2102N reference circuit, the VBUS (USB connector) and VBUS pin (CP2102N) are connected through a voltage divider resistor. This is to prevent the device from being damaged by a voltage exceeding its rating on the VUBS pin.

The CP2102N VBUS pin absolute maximum rating is

• 5.8V when VIO > 3.3V
• VIO+2.5V when VIO < 3.3V

stipulated in


Bus-Powered provides VBUS (5V) to VREGIN and an internal regulator to generate 3.3V for VDD (VIO). If the VBUS (USB connector) and VBUS pin (CP2102N) are directly connected, 5V will be applied to the VBUS pin shortly before 3.3V is generated. I will do it. Therefore, voltage dividing resistors are required.

Reference circuit when Bus-Powered (Excerpt from datasheet ver1.2)

In Self-Powered mode, if the CP2102N power supply is turned off while the USB cable is connected (5V is applied to the VBUS pin), the absolute maximum rating of the VBUS pin will still be violated. Therefore, voltage dividing resistors are required.

Reference circuit for Self-Powered (Excerpt from data sheet ver1.2)

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