NQB-N Datasheet, PDF (21/30 Pages) CUI INC – FULLY REGULATED ADVANCED BUS CONVERTERS

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CUI Inc │ SERIES: NQB-N │ DESCRIPTION: FULLY REGULATED ADVANCED BUS CONVERTERS
date 11/07/2014 │ page 21 of 30
automatically when the temperature has dropped below
the temperature threshold; the hysteresis is defined in
general electrical specification. The product has also an
under temperature protection.
Over Voltage Protection (OVP)
The product includes over voltage limiting circuitry for
protection of the load. The OVP limit is 30% above the
nominal output voltage. The response from an over
voltage fault is to immediately shut down. The device will
continuously check for the presence of the fault condition,
and when the fault condition no longer exists the device
will be re-enabled.
Over Current Protection (OCP)
The product includes current limiting circuitry for
protection at continuous overload. The setting for the
product is hic-up mode if the maximum output current is
exceeded and the output voltage is below 0.3×V_out. Above
the trip voltage the product will continue operate while
maintaining the output current at the maximum output
current. The load distribution should be designed for the
maximum output short circuit current specified.
Droop Load Share variants (DLS) will enter hic-up mode,
with a trip voltage, 0.04×V_out. Above the trip voltage the
product will continue to operate while maintaining the
output current at the maximum output current
Input Over/Under voltage protection
The input of the product is protected from high input
voltage and low input voltage.
Pre-bias Start-up Capability
The product has a Pre-bias start up functionality and will
not sink current during start up if a Pre-bias source is
present at the output terminals. If the Pre-bias voltage
is lower than the target value, the product will ramp up
to the target value. If the Pre-bias voltage is higher than
the target value, the product will ramp down to the target
value and in this case sink current for a limited time.
Output Voltage Regulation
The NQB products are designed to be fully regulated
within the plotted area. Operating outside this area is not
recommended.
Thermal Consideration
General
The product is designed to operate in different thermal
environments and sufficient cooling must be provided
to ensure reliable operation. For products mounted on
a PWB without a heat sink attached, cooling is achieved
mainly by conduction, from the pins to the host board,
and convection, which is dependant on the airflow across
the product. Increased airflow enhances the cooling of
the product. The Output Current Derating graph found in
the output section for each model provides the available
output current vs. ambient air temperature and air velocity
at V_I =53 V.
The product is tested on a 254 x 254 mm, 35 µm (1 oz),
16-layer test board mounted vertically in a wind tunnel
with a cross-section of 608 x 203 mm.
For products with base plate used in a sealed box/cold
wall application, cooling is achieved mainly by conduction
through the cold wall. The Output Current Derating graphs
are found in the output section for each model. The
product is tested in a sealed box test set up with ambient
temperatures 85, 55 and 25°C.
13.4
13.2
13.0
12.8
12.6
12.4
12.2
12.0
35 45 55 65 75
Vin [V]
Vin range: 36-75Vdc
13.4
13.2
13.0
12.8
12.6
12.4
12.2
12.0
35 40 45 50 55 60 65
Vin [V]
Vin range:40-60Vdc
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