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10
4.
Protective measures
Protective measures against electrostatic discharge
Modern semiconductor devices are increasingly endangered by electrostatic charges. The higher the integration
density the finer the structures on the chip. This leads to increased stress susceptibility.
With certain semiconductor devices, damage may already be caused at a voltage of less than 20V. This is a very
low value if you consider that, when walking over a carpet, more than 1000V may be generated.
Damage caused by electrostatic discharge only rarely leads to an immediate total failure. The semiconductor
structures are only affected to such a degree that the function is still available. However, a "burning trace" laid
once initiates a chemical process on the chip, which only makes the component unusable after a longer time
(possibly after several months).
Protection against electrostatic charge
The generating of electrostatic charging can generally not be avoided. The only possibility is, therefore, to protect
the electronics from such dangerous voltages.
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Discharge yourself by touching a suitable object (e.g., heating, water pipe, etc.)
in the immediate vicinity before starting to work on endangered parts.
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Use only soldering irons that are galvanically separated from the power supply and equipped
with an electronic temperature control.
Protective measures against overvoltages - transients
A protective shielding and grounding must be provided in order to avoid malfunctions and the destruction of
system components due to atmospheric overvoltage, indirect or conditionally direct effects of thunderstorms. See
DIN VDE 0845 part 1, Protection of telecommunication systems against lightning strokes, static charges and
overvoltages caused by power installations - measures against overvoltages.
A basic protection or a fine protection has already already been integrated into the corresponding devices by
Novar GmbH according to VdS requirements.
Complete protection against damage caused by lightning strokes and overvoltages is assured by the measures
taken for the external and internal lightning protection. The overvoltage protection is also called medium and
coarse protection. The consideration of additional requirements and measures for the installation of system
components mainly depends on the installation site and the equipment connected to the system.
Overvoltage caused, for example, by switching actions causes a very steep rise of voltage. This means that the
voltage can reach values of several kV within a few µs. Such voltage pulses are also called transients. They are
responsible for the destruction of electronic components.
Overvoltage protection means suitable measures which enable the absorption of such transients.
Causes of transient interference voltages
Transient voltages are often caused by atmospheric discharge, i.e., a lightning stroke. A lightning discharge may
release currents reaching maximum values of 100kA and more with very short rise times. This lightning current
causes a high voltage drop of the earth resistance of the building and the high lightning current steepness induces
high voltages in conductive loops.
The energy resulting from a lightning discharge causes the destruction of unprotected devices. Switching actions
in electrical systems also cause overvoltages.
High-frequency compensation processes in power supply networks are continued on high-voltage lines and are
coupled in the low-voltage level. Overvoltages and high-frequency istil
nterference power transients in low-voltage installations may also be caused by voltage drops, phase control, etc.
The rate of raise of current may even reach higher values than a lightning stroke.
Installation instructions / ACS-2 plus
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