What should be done with USB pins if the module is not used?
The following are the recommended connections for unused USB pins when the USB device is not connected to the host and the USB module on the device is not enabled:
|VBUS||May be left unconnected / floating.|
|VUSB||Even when the USB module is not enabled, connect directly to Vdd with a bypass capacitor on it (10uF max) to limit the inrush current into the device.|
|D+/D-||Configure as output pins driven to either state (high or low), or configure as an input with an external resistor (about 10KΩ) pulling it to Vdd or Vss. If configured as an input, only the pin input leakage current will be drawn through the pins (the same current would flow if the pin was connected directly to Vdd or Vss). Both options allow the pins to be used later for either input or output without significant hardware modifications.|
|USBID||Configure as an output pin driving to either state (high or low), or configure as an input with an external resistor (about 10KΩ) pulling it to Vdd or Vss.|
Microchip Technology acquires Atmel