PRELIMINARY
Application Information
(continued)
OVP 鈥?Overvoltage Protection
The output Overvoltage Protection set point of the P048K048T24AL is
factory preset for 58 V. If this threshold is exceeded the output shuts
down and a restart sequence is initiated. If the condition that causes
OVP is still present, the unit will again shut down. This cycle will be
repeated until the fault condition is removed. The OVP set point may
be set at the factory to meet unique high voltage requirements.
PRM output power versus VTM output power
As shown in Figure 15, the P048K048T24AL is rated to deliver 5 A
maximum, when it is delivering an output voltage in the range from
26 V to 48 V, and 240 W, maximum, when delivering an output
voltage in the range from 48 V to 55 V. When configuring a PRM for
use with a specific VTM, refer to the appropriate VTM data sheet. The
VTM input power can be calculated by dividing the VTM output power
by the VTM efficiency (available from the VTM data sheet). The input
power required by the VTM should not exceed the output power
rating of the PRM.
100.00
V鈥 Chip Pre-Regulator Module
Adjusting current limit
The current limit can be lowered by placing an external resistor
between the I
L
and SG ports (see figure 16 for resistor values). With
the I
L
port open-circuit, the current limit is preset to be within the
range specified in the output specifications table on Page 4.
Resistance (k惟)
10.00
1.00
1
5.1
5.0
4.9
2
3
4
5
Desired PRM Output Current Limit (A)
Figure 16
鈥?External resistor value for adjusting current limit
Current (A)
4.8
4.7
4.6
4.5
4.4
4.3
Safe Operating Area
Input fuse recommendations
A fuse should be incorporated at the input to the PRM, in series with
the +IN port. A fast acting fuse, NANO2 FUSE 451/453 Series 10 A
125 V, or equivalent, may be required to meet certain safety agency
Conditions of Acceptability. Always ascertain and observe the safety,
regulatory, or other agency specifications that apply to your specific
application.
Product safety considerations
If the input of the PRM is connected to SELV or ELV circuits, the output
of the PRM can be considered SELV or ELV respectively.
0
~
~
20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60
Factorized Bus Voltage (V
f
)
Figure 15
鈥?P048K048T24AL rating based on Factorized Bus voltage
The Factorized Bus voltage should not exceed an absolute limit of
55 V, including steady state, ripple and transient conditions. Exceeding
this limit may cause the internal OVP set point to be exceeded.
Parallel considerations
The PR port is used to connect two or more PRMs in parallel to form a
higher power array. When configuring arrays, PR port interconnection
bypass capacitance must be used at ~1nF per PRM. Additionally one
PRM should be designated as the master while all other PRMs are set
as slaves by shorting their SC pin to SG. The PC pins must be directly
connected (no diodes) to assure a uniform start up sequence. The
factorized bus should be connected in parallel as well.
If the input of the PRM is connected to a centralized DC power system
where the working or float voltage is above SELV, but less than or
equal to 75 V, the input and output voltage of the PRM should be
classified as a TNV-2 circuit and spaced 1.3 mm from SELV circuitry or
accessible conductive parts according to the requirements of UL60950,
CSA 22.2 60950, EN60950, and IEC60950.
Applications assistance
Please contact Vicor Applications Engineering for assistance,
1-800-927-9474, or email at apps@vicr.com.
vicorpower.com
800-735-6200
V鈥 Chip Pre-Regulator Module
P048K048T24AL
Rev. 1.4
Page 10 of 15
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