JFC050C Datasheet, PDF (13/20 Pages) Tyco Electronics – dc-dc Converters; 18 to 36 Vdc Input; 15 Vdc Output; 50 W to 100 W

Data Sheet
October 1999
JFC050C, JFC075C, JFC100C Power Modules:
dc-dc Converters; 18 to 36 Vdc Input, 15 Vdc Output; 50 W to 100 W
Feature Descriptions (continued)
Thermal Warning
Output Current Monitor
The current monitor (CURMON) pin produces a dc volt-
age proportional to the dc output current of the module.
The voltage is referenced to the secondary SENSE(–)
pin and is typically 4.8 V at rated output current. For
paralleling with Fx300x modules, consult the factory for
the V/A ratio. The output impedance of this pin is
approximately 20 k¾, so customer detection circuitry
must have a high-impedance input.
The thermal warning (TEMPWARN) pin is a second-
ary-referenced, open-collector output that shorts to
SENSE(–) a few degrees before the module goes into
thermal shutdown. When the module temperature
cools, the thermal warning pin will open, but the unit
will remain latched off until the input power or the pri-
mary or secondary referenced remote on/off is recy-
cled for 1.0 second.
Thermal Considerations
Overtemperature Protection
To provide protection in a fault condition, the unit is
equipped with a thermal shutdown circuit. The shut-
down circuit will not engage unless the unit is operated
above the maximum case temperature. Recovery for
the thermal shutdown is accomplished by cycling the
dc input power off for at least 1.0 second or by toggling
the primary or secondary referenced remote on/off sig-
nal for at least 1.0 second.
Introduction
The JFC-Series power modules operate in a variety of
thermal environments; however, sufficient cooling
should be provided to help ensure reliable operation of
the units. Heat-dissipating components inside the units
are thermally coupled to the case. Heat is removed by
conduction, convection, and radiation to the surround-
ing environment. Proper cooling can be verified by
measuring the case temperature. Peak temperature
(TC) occurs at the position indicated in Figure 18.
Power Good Signal
The power good signal (PWRGOOD pin) is an open-
collector, secondary-referenced pin that is pulled low
when all five of the following conditions are met:
1. The sensed output voltage is greater than half the
rated nominal output voltage.
2. The overvoltage shutdown latch is not set.
3. The thermal shutdown latch is not set.
4. The unit is not in current limit.
5. Secondary internal bias is present.
There is one situation where the power good signal can
be low even though the module has failed. This can
occur when the module is paralleled with other mod-
ules for additional output power (i.e., the output ORing
diodes would not be used). If one module power train
stops delivering power (fails), the other paralleled mod-
ule(s) would provide a voltage at the output pin of the
failed module. The failed module would then not detect
that its output power was not being delivered. However,
in this situation the current monitor pins of the paral-
leled modules would indicate that current is not being
delivered from one module and that module had failed.
For redundant applications, the ORing diodes would
keep the other module voltages from being applied to
the failed module output and the power good signal
would indicate a failure.
Tyco Electronics Corp.
7.6 (0.30)
38.0 (1.50)
MEASURE CASE
TEMPERATURE HERE
8-1397 (C).a
Note: Top view, measurements shown in millimeters and (inches).
Pin locations are for reference.
Figure 18. Case Temperature Measurement
Location
The temperature at this location should not exceed
100 °C. The output power of the module should not
exceed the rated power for the module as listed in the
Ordering Information table.
Although the maximum case temperature of the power
modules is 100 °C, you can limit this temperature to a
lower value for extremely high reliability.
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