EMX Protection Resistors

NETMF & Gadgeteer
1

Just starting out with an EMX board design, and I have some preliminary questions…

  1. The manual says to connect the USB VBUS to UD_VBUS via a protection resistor, but neither the EMX-DEV or Cobra schematics show this. Is a resistor required, and if so what value?

  2. The manual says to connect LMODE to GND with a 10k resistor. The EMX-DEV board has this, but the Cobra has a 2.2k instead. Is there a reason? Which should I use?

  3. I haven’t seen anything that states what there is in the way of buffers, level shifters, protection circuitry, etc between the pins on the LPC2478 and the corresponding pins on the EMX module. Is there any, or are the lines routed out directly?

  4. The LPC2478 has separate connections for analog and digital supply and ground, are these taken out to specific connections on the EMX module, or are all the 3.3V/GND pins common?

Thanks,
David

2

Good questions

  1. There is a 10K on the module itself for UD_VBUS pin. I think this was planned to be changed to you can use any pin you like but then you need to add a resistor 1K to 10K is fine.

  2. 10K is lower power but 2.2K is better. Any value will be fine.

  3. processor to pads directly.

  4. no specific pins