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Overvoltage Protection
There are several recommended over-
voltage protection options. The applica-
tion will determine the most appropriate
one to chose (e.g. in-house only systems
with minimal protection requirements,
or systems with loops outside a protect-
ed environment requiring more extend-
ed protection).
The first external protection network to
protect the line circuit against foreign
voltages consists of the resistors Rpr1
and Rpr2 and an overvoltage protec-
tion component, see fig 5. The series
resistors Rpr1 and Rpr2 can be PTC,
poly-switch or fusible components.
Rpr1
GNDB
Rpr2
Rpr1
GNDB
Rpr2
Fig. 5: Recommended overvoltage protection options
For further protection, the simplest and
cheapest solution is a diode bridge
between SA,SB and GNDB, BATR
respectively. The diodes must be able to
allow current peaks more then 20A.
In case the battery BATR cannot accept
these high current peaks, one has to
add a voltage clamping component to
GND or a transient suppresser between
each line and GND. The clamp voltage
or protection voltage minimum must
always be larger then the maximum
used ringing battery BATR.
The protection components must be
dimensioned in such a way that the
transient energy on the chip pins AW,
BW does not exceed 1mJoule.(energy
on chip because of 1 lightning pulse)
SA
AW
RB1
BATR
MTC-30132
SH LIC
BW
RB2
SB
SA
AW
RB1
MTC-30132
SH LIC
BW
RB2
SB
13
MTK-40131
Rpr1
RB1
GNDB
Rpr2
RB2
Rpr1
RB1
Transient
GNDB
Suppressor
Rpr2
RB2
SA
AW
MTC-30132
SH LIC
BW
SB
SA
AW
MTC-30132
SH LIC
BW
SB
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