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16-
03
10
Z-System – Zener Barriers
Product Specifications
The following figure shows the flow of leakage current through the zener diodes
by using an example of a zener barrier with 24 V and 300
. Under normal
circumstances the zener barrier conducts a maximum of 10
µ
A leakage current
so long as the supply voltage is less than 25.5 V. This is normal and has very little
effect on the load.
If the voltage exceeds 25.5 V, the zener diodes start to conduct more current.
This can have an effect on the operating current and the accuracy. It is
recommended that a regulated voltage source be used, which maintains the
voltage under the value at which the diodes will start to conduct. These voltages
are stated in the datasheet for a given zener barrier, together with the leakage
current. If the leakage current for a given voltage differs from 10
µ
A (i. e. 1
µ
A),
this is specifically stated.
Figure 2.4
Leakage current through the zener diodes
The following figure shows that if the maximum permissible input (supply) voltage
is exceeded, the total current drains through the zener diodes, without reaching
the hazardous area.
Fuchs zener barriers have a low series resistance, given by the sum of
the resistance (R) and the resistance value of the fuse (F). Due to the low series
resistance, an inadvertent short circuiting of the terminals on the filed side can
cause the fuse to open.
Zone 0, 1, 2
Div. 1, 2
(+)
(-)
50 mA
24 V
10 μA
Power
supply
Load
≤ 25.5 V