What to do with unused USB I/O pins on LPC2148?

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What to do with unused USB I/O pins on LPC2148?

Contributor II

I'm creating a design with the LPC2148 where I don't use the USB functionality.

What should I do with the following pins:

  • D+ (USB D+ Line), pin 10.
  • D- (USB D- Line), pin 11.

I need to avoid EMI because my board is used in industrial applications and noisy environments.

Can I leave the pins unconnected or should I tied to ground?

What is better for EMI ?

I looked in all the available datasheets and manuals but none of them are telling what to do when not using the USB peripherals.

Thanks in advance

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NXP TechSupport
NXP TechSupport

Hello  Rodion,

   USB controller in LPC2148 is USB HOST, On D+ & D- Lines, there is a 15k pull down resistor respectively.
It means when there is no USB device inserted, D+ & D- will be kept LOW level. So if you don't use USB HOST,
it is no problem to float them, and there is no effect for EMC. it is not recommended to connect them to GND,
because in comparison to Floating them, there is no more help for improving EMC performance.

Have a nice day!
TIC weidong

Contributor II

Thanks Wigros Sun !

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