20IMX4-12-8 Datasheet, PDF (7/12 Pages) Power-One – IMX4 Series Data Sheet 4 Watt DC-DC Converters

IMX4 Series Data Sheet
®
4 Watt DC-DC Converters
Thermal Considerations
If a converter, mounted on a PCB, is located in free, quasi-
stationary air (convection cooling) at the maximum ambient
temperature T_{A max} (see table Temperature specifications)
and is operated at nominal input voltage and output power,
the case temperature T_C measured at the measuring point of
case temperature T_C (see Mechanical Data) will approach the
indicated value T_{C max} after the warm-up phase. However, the
relationship between T_A and T_C 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. T_{A max} is
therefore only an indicative value, and under practical
operating conditions, the ambient temperature T_A may be
higher or lower.
Caution: The case temperature T_C measured at the measuring
point of case temperature T_C (see Mechanical Data) may under no
circumstances exceed the specified maximum. The installer must
ensure that under all operating conditions T_C remains within the
limits stated in the table Temperature Specifications.
Short Circuit Behavior
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.
V_o [%]
100
70
05041a
overload short circuit condition
switch-off
0
Fig. 9
Overload switch-off (hiccup mode).
t [ms]
0.3 s
Connection in Parallel
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
V_o [V]
5.25
05056b
5.0
4.75
4.5
4.25
4.0
0
Fig. 10
I_o
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 A
V_o versus I_o (typ) of single-output models (20IMX4-05)
V_o1 + V_o2 [V]
31.5
05057a
31
30.5
30
29.5
29
28.5
0
20 40
I_o
60 80 100 120 140 mA
Fig. 11
V_o versus I_o (typ.) of dual-output models (±15 V), with load
connected between Vo+ and Vo –.
Output Overvoltage Protection
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.
Connection in Series
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.
V_o1 [V]
16.5
05058a
16
15.5
15
14.5
14
0
I_o2 = 140 mA
I_o2 = 14 mA
I_o1
20 40 60 80 100 120 140 mA
Fig. 12
Cross load regulation of dual-output models. V_o1 versus I_o1
(typ) for various I_o2 (40IMX4-1515).
BCD20006-G Rev AC, 06-Jul-2012
Page 7 of 12
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