ATAM510X-ILQY ATMEL [ATMEL Corporation], ATAM510X-ILQY Datasheet - Page 59

• Manufacturer Part Number: ATAM510X-ILQY
• Description: MARC4 4-bit MTP Universal Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

3.8
3.8.1
3.8.2
4711B–4BMCU–01/05
Noise Considerations
Noise Immunity
Electromagnetic Emissions
When designing the microcontroller based application, several factors should be taken into con-
sideration to increase noise immunity and reduce electromagnetic emissions (EME). Many such
potential problems can be avoided by careful layout of the printed circuit board (PCB). The PCB
contains many parasitic components which at first sight are not apparent. PCB tracks can act as
antennas or as coupling capacitors. Long stretches of parallel tracks and long high frequency
signal lines should thus be avoided wherever possible to minimize the chance of picking up or
transmitting unwanted signals.
The following guidelines will increase system noise immunity:
Electromagnetic emissions are caused by rapidly changing electrical currents (dI/dt) in long
antenna like connection lines and cables. This can result in electrical interference on other tele-
communication devices. These current spikes are more often than not present in the system
power supply lines and driver signal lines.
The following guide will help to reduce EME:
• Unconnected inputs should not be left open. If port pins are not required then it is
• Special care should be taken when laying out the PCB that interrupt, reset and clock signal
• A quartz crystal should always be located right next to the microcontroller crystal oscillator
• PCB's should, where economically possible, be equipped with adequate ground planes.
• The microcontroller power supply should be decoupled with an electrolytic capacitance
• Keep the length of PCB current switching signal tracks to a minimum..
• Adopt a PCB star power routing system connected at one point.
• Many of the microcontroller port outputs can be configured with several drive strengths. This
• If possible, write the application program to avoid multiple outputs switching at any instant.
• Cables can be equipped with ferrite rings to slow current spikes or the system can be
recommended to set pull-up or pull-down options on these pins.
lines are kept short and are carefully shielded or have sufficient spacing from other on board
noise generating sources.
terminals (OSCIN and OSCOUT), the connections being always very short. This avoids, not
only signal coupling onto the clock source, but can also reduces EME.
(approximate 10 µF) in parallel with a ceramic capacitance (approximate 100 nF) situated as
close to the microcontroller device as possible.
means that a high drive output will switch a signal faster than for example a standard drive
output. The resulting change in current in the signal and power lines will also increase,
causing an increase in EME. So wherever speed and drive current is not necessary the ports
should be configured with the lowest drive possible.
encased in a grounded conducting casing.
ATAM510
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