IMX4 Series Data Sheet
4 Watt DC-DC Converters
®
Thermal Considerations
Connection in Parallel
If a converter, mounted on a PCB, is located in free, quasi-
stationary air (convection cooling) at the maximum ambient
temperature TA max (see table Temperature specifications)
and is operated at nominal input voltage and output power,
the case temperature TC measured at the measuring point of
case temperature TC (see Mechanical Data) will approach the
indicated value TC max after the warm-up phase. However, the
relationship between TA and TC depends heavily on the
conditions of operation and integration into a system. The
thermal conditions depend on input voltage, output current,
airflow, temperature of surrounding components and surfaces
and the properties of the printed circuit board. TA max is
therefore only an indicative value, and under practical
operating conditions, the ambient temperature TA may be
higher or lower.
Several converters with equal output voltage can be
connected in parallel and will share their output current quite
equally. However, this may cause start-up problems and is only
recommended in applications, where one converter is able to
deliver the full load current, e.g., in true redundant systems.
Typical Performance Curves
Vo [V]
05056b
5.25
5.0
4.75
4.5
Caution: The case temperature TC measured at the measuring
point of case temperature TC (see Mechanical Data) may under no
circumstances exceed the specified maximum. The installer must
ensure that under all operating conditions TC remains within the
limits stated in the table Temperature Specifications.
4.25
Io
4.0
0
0.1
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A
0.2
Fig. 10
Short Circuit Behavior
Vo versus Io (typ) of single-output models (20IMX4-05)
The current limitation shuts down the converter, when a short
circuit is applied to the output. It acts self-protecting, and
automatically recovers after removal of the overload condition.
Vo1 + Vo2 [V]
05057a
31.5
31
05041a
Vo [%]
30.5
30
overload short circuit condition
100
switch-off
70
29.5
29
Io
28.5
0
20
40
60
80
100
120 140 mA
t [ms]
0
0.3 s
Fig. 11
Fig. 9
Vo versus Io (typ.) of dual-output models (±15 V), with load
connected between Vo+ and Vo–.
Overload switch-off (hiccup mode).
Vo1 [V]
Output Overvoltage Protection
05058a
16.5
The outputs are protected against overvoltages by Zener
diodes. In the event of an overvoltage, the converter will shut-
down and attempt to restart automatically. The main purpose
of this feature is to protect against possible overvoltages,
which could occur due to a failure in the feedback control
circuit. The converters are not designed to withstand external
overvoltages applied to the outputs.
16
15.5
Io2 = 140 mA
15
Io2 = 14 mA
14.5
Connection in Series
Io1
140 mA
14
The outputs of single or dual-output models can be connected
in series without any precautions, taking into consideration
that the output voltage should remain below 60 V for SELV
operation.
0
120
20
40
60
80
100
Fig. 12
Cross load regulation of dual-output models. Vo1 versus Io1
(typ) for various Io2 (40IMX4-1515).
BCD20006-G Rev AC, 06-Jul-2012
Page 7 of 12
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