
Board Mountable
DC-DC Converters
IMX 35 Series
Edition 3/4.2000
7/18
Inrush current
The inrush current has been kept as low as possible by
choosing a very small input capacitance. A series resistor
may be installed in the input line to further reduce this cur-
rent.
I [A]
t [
s]
04022
0
10
20
30
40
50
60
70
80
90 100
4
3
2
1
Fig. 4
Typical inrush current at Ui nom, Po nom versus time
(40 IMX 35). Source impedance according to
prETS 300132-2, version 4.3 at Ui nom.
Fig. 5
Converter start-up and rise time
Uo nom
Uo
tstart up
trise
t
04008
Input Transient Voltage Protection
A built-in suppressor diode provides effective protection
against input transients which may be caused for example
by short-circuits accross the input lines where the network
inductance may cause high energy pulses.
Table 4: Built-in transient voltage suppressor
Type
Breakdown
Peak power
Peak pulse
voltage
at 1 ms
current
VBr nom [V]
Pp [W]
Ipp [A]
20 IMX 35
50
1500
22
40 IMX 35
100
1500
9.7
For very high energy transients as for example to achieve
IEC/EN 61000-4-5 or ETR 283 (19 Pfl1) compliance (as per
table:
Electromagnetic Immunity) an external inductor and
capacitor are required. The components should have simi-
lar characteristics as listed in table:
Components for exter-
nal circuitry for IEC/EN 61000-4-5, level 2 or ETR 283
(19Pfl1) compliance.
Note: The suppressor diode D is only necessary for
20 IMX 35 types.
Table 5: Components for external circuitry for IEC/EN
61000-4-5, level 2 or ETR 283 (19Pfl1) compliance.
Type
Inductor (L)
Capacitor (C)
Diode (D)
20 IMX 35
22
H/5A
470
F/40 V
1.5 k E47A
40 IMX 35
68
H/2.7 A
2 x 100
F/100 V
-
Vi+
Vi–
C
L
D
+
04036
Fig. 6
Example for external circuitry to comply with IEC/EN
61000-4-5 or ETR 283 (19Pfl1); the diode D is only neces-
sary for 20 IMX 35 types.
Reverse Polarity Protection
The built-in suppressor diode also provides for reverse po-
larity protection at the input by conducting current in the re-
verse direction. An external fuse is required to limit this cur-
rent.
Table 3: Recommended external fuses
Converter type
Fuse type
20 IMX 35
F8.0A
40 IMX 35
F4.0A
22
23.8
11.5
04052
Fig. 7
Dimensions of inductor L for 20 IMX 35 and 40 IMX 35
types (e.g. Coil Craft, PCH-45 series).