PEB 2023
PEF 2023
Overview
Semiconductor Group
14
08.97
1.6
In telephone and ISDN-systems the topic “surge protection“ or “l(fā)ightning overvoltage
protection“ is very important. For the PEB/F 2023 overvoltage protection is necessary
when the DC/DC converter input supply voltage V
IN
is connected to the U- or S-interface-
lines.
Figure 7
shows how to protect the PEB/F 2023 when using supply voltage range 3 (see
also figure 4). For supply voltage ranges 1 and 2 the principle is the same.
Surge Protection
Figure 7
PEB/F 2023 Surge Protection
The DC/DC converter begins operating when the input voltage exceeds V
ZD1
+8V+V
RVs
.
In the start-up phase the PEB/F 2023 is supplied through V
S
. After this start-up phase,
the PEB/F 2023 is supplied via V
EXT
(power housekeeping input, see figure 4) and the
DC/DC-converter will operate until the input voltage falls below 20V (input undervoltage
detection).
The current i
LVR
needed in the start-up phase is less than 500
μ
A. With this current and
the value of resistor R
Vs
the voltage V
RVs
can be calculated.
For static and transient currents i
UV
and i
UVx
, respectively, absulote maximum ratings are
valid. Because of the high value of R
6
(for power saving reasons), i
UV
and i
UVx
normally
are sufficiently low.
Limits for voltage and current on pin V
S
are also defined in the maximum ratings.
PEB 2023
PEF 2023
3
7
GND
11
12
UV
V
S
+
0 V
BZV55C30
UVx
R
6
10Μ/10%
C
6
100μF
20%
ZD
1
R
Vs
i
Vs
i
UV
i
UVx
9.4V
9.4V
UV
1.2V
100V
ZD
p
LVR
i
LVR
5
V
EXT
V
IN
Overvoltage
protection
UV ... Undervoltage detection circuit
LVR ... Linear voltage regulator
ZD ... parasitic zener diode