®
IMX35 Series Data Sheet
35 Watt Quad-Output DC-DC Converters
Thermal Considerations
If a converter, mounted on a PCB, is located in free, quasi-
stationary air (convection cooling) at the indicated maximum
ambient temperature
T
A max
(see table
Temperature specifi-
cations)
and is operated at its nominal input voltage and output
power, the case temperature
T
C
(T
C Z
with option Z) measured
at the measuring point of case temperature (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 are influenced by input
voltage, output current, airflow, temperature of surrounding
components and the surfaces and 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 than this value.
Caution:
The case temperature
T
C
(or T
C Z
) measured at the
measuring point of case temperature (see
Mechanical Data)
may
under no circumstances exceed the specified maximum value.
The installer must ensure that under all operating conditions
T
C
(or
T
C Z
) remains within the limits stated in the table
Temperature
specifications.
V
o
[%]
overload short-circuit condition
100
70
switch-off
05041b
0
0.3 s
t
Fig. 6
Overload switch off (hiccup mode), typical values.
Series and Parallel Connection
The outputs of one or several double-output power trains may
be connected in series respecting the current limitation.
Both outputs of the same power train can always be
connected in parallel in will behave like a single output.
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.
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 24 V shall be generated by a converter with four
12 V outputs; see fig. 7.
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.
P
o
/P
o max
11047-X35a
1.0
0.8
0.5 m/s = 100 LFM
JM138
IMX35D12D12-9
Vi+
4
PUL
1
Trim
5
W
6
16
Vo1+
0.6
natural cooling
0.4
0.2
0
20
40
60
80
100
°C
T
A
15
Vo1–
Vo4+
PWM
17
Ref
7
SD
8
Vi–
2
n.c.
3
13
18
Vo4–
–24V
Fig. 5
Maximum allowed output power versus ambient
temperature.
Vo2+
+24V
14
12
Vo2–
Vo3+
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.
11
Vo3–
19
n.c.
Fig. 7
Generating 24 V with an IMX35D12D12-9
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 resistive and
capacitive load current, as it is required in true redundant systems.
Short Circuit Behavior
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).
BCD20009-G Rev AC, 06-May-2013
Page 7 of 15
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