Data Sheet
EQW012/020/023/025 Series, Eighth-Brick Power Modules:
36 - 75Vdc Input; 1.2Vdc to 5Vdc Output; 12A to 25A Output
December 12, 2008
operation this temperature should not exceed 115 oC.
The output power of the module should not exceed
the rated power for the module (Vo, set x Io, max).
Feature Description (Continued)
Overcurrent Protection
Tref
To provide protection in a fault (output overload)
condi¬tion, the module is equipped with internal
current-limiting circuitry, and can endure current
limiting continuously. At the instance of current-limit
inception, the output current begins to tail-out. When
an overcurrent condition exists beyond a few
seconds, the module enters a “hiccup” mode of
opera¬tion, whereby it shuts down and automatically
attempts to restart upon cooling. While the fault
condition exists, the module will remain in this hiccup
mode, and can remain in this mode until the fault is
cleared. The unit operates normally once the output
current is reduced back into its specified range.
Air Flow
Figure 43. Tref Temperature Measurement
Location.
Output Over Voltage Protection
The output overvoltage protection clamp consists of
control circuitry, independent of the primary regulation
loop, that monitors the voltage on the output
terminals. This control loop has a higher voltage set
point than the primary loop (See the overvoltage
clamp values in the Feature Specifications Table). In
a fault condition, the overvoltage clamp ensures that
the output voltage does not exceed Vo,ovsd, max.
This provides a redundant voltage-control that
reduces the risk of output overvoltage.
Please refer to the Application Note “Thermal
Characterization Process For Open-Frame Board-
Mounted Power Modules” for a detailed discussion of
thermal aspects including maximum device
temperatures.
Heat Transfer via Convection
Increased airflow over the module enhances the heat
transfer via convection. Derating figures showing the
maximum output current that can be delivered by
each module versus local ambient temperature (TA)
for natural convection and up to 2m/s (400 ft./min) are
shown in the respective Characteristics Curves
section.
Input Undervoltage Lockout
At input voltages below the input undervoltage lockout
limit, the module operation is disabled. The module
will begin to operate at an input voltage between the
undervoltage lockout limit and the minimum operating
input voltage.
Overtemperature Protection
To provide protection under certain fault conditions,
the unit is equipped with a thermal shutdown circuit.
The unit will shutdown if the thermal reference point
Tref (Figure 43), exceeds 125oC (typical), but the
thermal shutdown is not intended as a guarantee that
the unit will survive temperatures beyond its rating.
The module will automatically restarts after it cools
down.
Thermal Considerations
The power modules operate in a variety of thermal
environments; however, sufficient cooling should be
provided to help ensure reliable operation.
Considerations include ambient temperature, airflow,
module power dissipation, and the need for increased
reliability. A reduction in the operating temperature of
the module will result in an increase in reliability. The
thermal data presented here is based on physical
measurements taken in a wind tunnel.
The thermal reference point, Tref used in the
specifications is shown in Figure 43. For reliable
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