PTEA415050

SLTS291B – JULY 2008 – REVISED NOVEMBER 2010

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APPLICATION INFORMATION

Operating Features and System Considerations for the PTEA415050 DC/DC Converter

Overcurrent Protection

To protect against load faults, these converters incorporate output overcurrent protection. Applying a load to the

output that exceeds the converter's overcurrent threshold (see applicable specification) will cause the output

voltage to momentarily fold back, and then shut down. Following shutdown the module will periodically attempt to

automatically recover by initiating a soft-start power-up. This is often described as a hiccup mode of operation,

whereby the module continues in the cycle of successive shutdown and power up until the load fault is removed.

Once the fault is removed, the converter automatically recovers and returns to normal operation.

Output Overvoltage Protection

Each converter incorporates protection circuitry that continually senses for an output overvoltage (OV) condition.

The OV threshold is set approximately 20% higher than the nominal output voltage. If the converter output

voltage exceeds this threshold, the converter is immediately shut down and remains in a latched-off state. To

resume normal operation the converter must be actively reset. This can only be done by momentarily removing

the input power to the converter. For fail-safe operation and redundancy, the OV protection uses circuitry that is

independent of the converter’s internal feedback loop.

Overtemperature Protection

Overtemperature protection is provided by an internal temperature sensor, which closely monitors the

temperature of the converter’s printed circuit board (PCB). If the sensor exceeds a temperature of approximately

115°C, the converter will shut down. The converter will then automatically restart when the sensed temperature

drops back to approximately 105°C. When operated outside its recommended thermal derating envelope (see

data sheet SOA curves), the converter will typcially cycle on and off at intervals from a few seconds to one or two

minutes. This is to ensure that the internal components are not permanently damaged from excessive thermal

stress.

Undervoltage Lockout

The Undervoltage lockout (UVLO) is designed to prevent the operation of the converter until the input voltage is

at the minimum input voltage. This prevents high start-up current during normal power-up of the converter, and

minimizes the current drain from the input source during low input voltage conditions. The UVLO circuitry also

overrides the operation of the Remote On/Off control.

Primary-Secondary Isolation

These converters incorporate electrical isolation between the input terminals (primary) and the output terminals

(secondary). All converters are production tested to a withstand voltage of 1500 VDC. This specification complies

with UL60950 and EN60950 requirements. This allows the converter to be configured for either a positive or

negative input voltage source. The data sheet Pin Descriptions section provides guidance as to the correct

reference that must be used for the external control signals.

Input Current Limiting

The converter is not internally fused. For safety and overall system protection, the maximum input current to the

converter must be limited. Active or passive current limiting can be used. Passive current limiting can be a fast

acting fuse. A 125-V fuse, rated no more than 10 A, is recommended. Active current limiting can be implemented

with a current limited Hot-Swap controller.

Thermal Considerations

Airflow may be necessary to ensure that the module can supply the desired load current in environments with

elevated ambient temperatures. The required airflow rate may be determined from the Safe Operating Area

(SOA) thermal derating chart (see typical characteristics).

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