IMX35 Series Data Sheet
35 Watt Quad-Output DC-DC Converters
®
Thermal Considerations
Short Circuit Behavior
If a converter, mounted on a PCB, is located in free, quasi-
stationary air (convection cooling) at the indicated maximum
ambient temperature TA max (see table Temperature specifi-
cations) and is operated at its nominal input voltage and output
power, the case temperature TC (TC Z with option Z) measured
at the measuring point of case temperature (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 are influenced by input
voltage, output current, airflow, temperature of surrounding
components and the surfaces and 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 than this value.
The current limit characteristic shuts down the converter
whenever a short circuit is applied to an output. It acts self-
protecting and automatically recovers after removal of the
overload condition (hiccup mode).
Vo [%]
overload short-circuit condition
100
switch-off
05041b
70
t
0
0.3 s
Caution: The case temperature TC (or TC Z) measured at the
measuring point of case temperature TC (see Mechanical Data)
may under no circumstances exceed the specified maximum
value. The installer must ensure that under all operating conditions
TC remains within the limits stated in the table Temperature
specifications.
Fig. 6
Overload switch off (hiccup mode), typical values.
The converters provide the specified output power with free air
convection cooling. In the upper temperature range the output
power derating below should be observed.
Series and Parallel Connection
The outputs of one or several double-output power trains may
be connected in series without any precaution.
Po/Po max
11047-X35a
Both outputs of the same power train can always be connected
in parallel in will behave like a single output.
1.0
0.8
Several outputs of the same converter with equal output
voltage (e.g., 5 V / 5 V) can be connected in parallel and will
share their output currents almost equally.
0.5 m/s
= 100 LFM
0.6
If outputs of the same converter are being parallel and series-
connected, it is recommended that outputs from the same
power trains are parallel-connected first. This applies for
instance, if 30 V shall be generated by a converter with four
15 V outputs.
natural cooling
0.4
0.2
0
TA
20
40
60
80
100
°C
Note: Parallel operation of several converters may cause start-up
problems. This becomes noticable in applications, where one
converter is not able to deliver allone the full load current, as it is
required in true redundant systems.
Fig. 5
Maximum allowed output power versus ambient
temperature.
Overtemperature Protection
The converter is protected against possible overheating by
means of an internal temperature monitoring circuit. It shuts
down the converter above the internal temperature limit and
attempts to automatically restart. This feature prevents
excessive internal temperature building up which could occur
under heavy overload conditions.
BCD20009-G Rev AB, 2-Mar-2011
Page 7 of 15
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