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LPC43xx schematic without USB

Question asked by Priit Tänav on Nov 9, 2019
Latest reply on Nov 12, 2019 by ZhangJennie

I am designing my first LPC MCU based circuit board.

I am using these two schematics as a guidance:

https://www.nxp.com/downloads/en/schematics/LPCX43xx_18xx_V3_Schematic_Rev-B.pdf 

https://www.nxp.com/downloads/en/schematics/LPC-Link2-SCH.pdf 

 

How do the USB pins

  • USB0_DP
  • USB0_DM
  • USB0_VBUS
  • USB0_ID
  • USB0_RREF
  • USB1_DP
  • USB1_DM
  • USB0_VDDA3V3_DRIVER
  • USB0_VDDA3V3
  • USB0_VSSA_TERM
  • USB0_VSSA_REF

have to be wired when USB functionality is not used?

 

Can they be:

a) left all unconnected?

b) USB0_VSSA_TERM and USB0_VSSA_REF connected to GND and others left unconnected?

c) or do I have to provide 3.3V to USB0_VDDA3V3 and USB0_VDDA3V3 with decoupling capacitors; and GND to USB0_VSSA_TERM and USB0_VSSA_REF even if USB functionality is not used?

 

Is there any difference relating to circuit design when comparing LPC43xx that has no USB functionality (e.g LPC431x) vs one that has (LPC433x etc), in case when USB functionality is not used? In particular, is it permissible to connect 3.3V to USB0_VDDA3V3 and USB0_VDDA3V3 for LPC431x that has no USB?

 

All information is welcome.

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