User manual

Code Mercenaries

10.0 ESD Considerations

IO-Warrior has an internal ESD protection to

withstand discharges of more than 2000V without

permanent damage. However ESD may disrupt

normal operation of the chip and cause it to exhibit

erratic behaviour.

For the typical office environment the 2000V

protection is normally sufficient. Though for

industrial use additional measures may be

necessary.

When adding ESD protection to the signals special

care must be taken on the USB signal lines. The

USB has very low tolerance for additional

resistance or capacitance introduced on the USB

differential signals.

Series resistors of 27 may be used alone or in

addition to some kind of suppressor device. In any

case the USB 2.0 specification chapter 6 and 7

should be read for detailed specification of the

electrical properties.

10.1 EMC Considerations

IO-Warrior uses relatively low power levels and so

it causes few EMC problems. The most important

issue is to provide a very clean layout for the

power supply. IO-Warrior runs at 12MHz internal

clock rate, this can cause current spikes if the

supply lines are not carefully layed out.

To avoid any EMC problems the following rules

should be followed:

• Keep the PCB traces from the resonator to the

chip pins as short as possible.

• Put the 100nF ceramic capacitor right next to

the power supply pins of the chip and make sure

the PCB traces between the chips power pins

and the capacitor are as short as possible.

• Run the power supply lines first to the capacitor,

then to the chip.

• Connect the second ground pin in the shortest

possible way to the first ground pin. No other

things may have precedence over this.

• Keep the two USB signal lines close to each

other, route no other signal between them. USB

uses differential signalling so the best signal

quality with lowest RF emission is achieved by

putting these lines very close to each other.

V 1.1.0, December 2nd 2013, for chip revision V1.0.3.0 and up