Trimming/sensing beyond 110% of the rated output voltage is not an acceptable design practice, as this condition could
cause unwanted triggering of the output overvoltage protection (OVP) circuit. The designer should ensure that the difference
between the voltages across the converter’s output pins and its sense pins does not exceed 10% of V
OUT
(nom), or:
X NOM-O SENSESENSEOUTOUT 10%V)](V)([V)](V)([V
[V]
This equation is applicable for any condition of output sensing and/or output trim.
Input undervoltage lockout is standard with this converter. The converter will shut down when the input voltage drops below
a pre-determined voltage.
The input voltage must be typically 34 V for the converter to turn on. Once the converter has been turned on, it will shut off
when the input voltage drops typically below 32 V. This feature is beneficial in preventing deep discharging of batteries used
in telecom applications.
The converter is protected against overcurrent or short circuit conditions. Upon sensing an overcurrent condition, the
converter will switch to constant current operation and thereby begin to reduce output voltage. When the output voltage
drops below 60% of the nominal value of output voltage, the converter will shut down.
Once the converter has shut down, it will attempt to restart nominally every 200 ms with a typical 3-5% duty cycle. The
attempted restart will continue indefinitely until the overload or short circuit conditions are removed or the output voltage
rises above 60% of its nominal value.
Once the output current is brought back into its specified range, the converter automatically exits the hiccup mode and
continues normal operation.
For implementations where latching is required, a “Latching” option (L) is available for short circuit and OVP protections.
Converters with the latching feature will latch off if either event occurs. The converter will attempt to restart after either the
input voltage is removed and reapplied OR the ON/OFF pin is cycled.
The converter will shut down if the output voltage across Vout(+) (Pin 8) and Vout(-) (Pin 4) exceeds the threshold of the OVP
circuitry. The OVP circuitry contains its own reference, independent of the output voltage regulation loop. Once the converter
has shut down, it will attempt to restart every 200 mS until the OVP condition is removed.
For implementations where latching is required, a “Latching” option (L) is available for short circuit and OVP protections.
Converters with the latching feature will latch off if either event occurs. The converter will attempt to restart after either the
input voltage is removed and reapplied OR the ON/OFF pin is cycled.
The converter will shut down under an overtemperature condition to protect itself from overheating caused by operation
outside the thermal derating curves, or operation in abnormal conditions such as system fan failure. After the converter has
cooled to a safe operating temperature, it will automatically restart for non-latching option.
Approved to the latest edition of the following safety standards: UL/CSA 60950-1, EN60950-1 and IEC60950-1. Basic
Insulation is provided between input and output.
To comply with safety agencies’ requirements, an input line fuse must be used external to the converter. A 10 A fuse is
recommended for use with this product.
All QME converters are UL approved for a maximum fuse rating of 15 Amps. To protect a group of converters with a single
fuse, the rating can be increased from the recommended value above.
