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V•I Chip Pre-Regulator Module

P048F048T24AL

Rev. 3.4

Page 10 of 14

V•I Chip Pre-Regulator Module

OVP – Overvoltage Protection

The output Overvoltage Protection set point of the P048F048T24AL is

factory preset for 56 V. If this threshold is exceeded the output shuts

down and a restart sequence is initiated, also indicated by PC pulsing.

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 17, the P048F048T24AL 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.

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 PRMs in parallel to form a higher

power array. When configuring arrays, PR port interconnection

terminating impedance is 10 k to SG. See note Page 8 and refer to

Application Note AN002. 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 minimum load current for slave PRMs is specified on

page 4. Users should ensure that all slave PRMs operate above the

specified minimum current in order to avoid the risk of failure. The PC

pins must be directly connected (no diodes) to assure a uniform start

up sequence. Consult Vicor applications engineering for applications

requiring more than two PRMs.

Adjusting Current Limit

The current limit can be lowered by placing an external resistor

range specified in the output specifications table on Page 4.

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.

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

UL60950-1, CSA 22.2 60950-1, EN60950-1, and IEC60950-1.

Application Notes

For PRM and V•I Chip application notes on soldering, board layout,

and system design please click on the link below:

http://www.vicorpower.com/technical_library/application_information/chips/

Applications Assistance

Please contact Vicor Applications Engineering for assistance,

1-800-927-9474, or email at apps@vicorpower.com.

DC CURRENT LIMIT

1

10

100

0123

456

Desired PRM Output Current Limit (A)

Figure 18 — Calculated external resistor value for adjusting current limit,

actual value may vary.

26

30

34

38

42

46

50

54

4.6

4.7

4.8

4.9

5.0

5.1

28

32

36

40

44

48

52

4.5

4.4

4.3

60

20

~

~

0

22 24

56 58

Safe Operating Area

Figure 17 — P048F048T24AL rating based on Factorized Bus voltage