Some NuMicro® family series that support USB function are provided with the internal LDO which can convert 5V input voltage of V_BUS into 3.3V output voltage and supply the 3.3V to a USB transceiver. When the USB function is used, the LDO output pin V_DD33 needs to connect to the LDO output voltage having a stable capacitor. Also, the capacitor needs to be close to the V_DD33 pin.

According to different NuMicro® Family series, the value of an external capacitor for V_DD33 may be different. Please refer to the following table:

NuMicro® Family Series	Minimum Value of an External Capacitor
NUC120 Series	1 uF
NUC140 Series	1 uF
NUC122 Series	1 uF
NUC123 Series	1 uF
NUC220 Series	1 uF
NUC240 Series	1 uF
Nano120/130 Series	1 uF
NUC442/472 Series	10 uF
M452/453 Series	1 uF
NUC505 Series	Do not have LDO for USB.

In consideration of chip operational stability, it is not recommended that LDO output be used to drive other external chips.

Products:	Microcontrollers ,Arm Cortex-M0 MCUs ,Nano120 USB Series ,Nano130 Advanced Series ,NUC120/122/123/220 USB Series ,NUC140/240 Connectivity Series ,Arm Cortex-M4 MCUs ,M452 USB Series ,M453 CAN Series ,NUC442/472 Series ,NUC505 Series
Applications:
Function:	Peripherals,Connectivity,USB,Power Detection,LDO

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Is the NuMicro® family chip provided with an internal LDO (Low Dropout Regulator) to supply 3.3V to a USB transceiver? Issue Date：2015-09-09

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