Lineage Power
9
Data Sheet
April 2008
dc-dc Converters; 36 to 75 Vdc Input, 2.5 Vdc Output; 125 W to 150 W
FW250G1 and FW300G1 Power Modules:
Feature Descriptions
Overcurrent Protection
To provide protection in a fault (output overload) condi-
tion, the unit is equipped with internal current-limiting
circuitry and can endure current limiting for an unlim-
ited duration. At the point of current-limit inception, the
unit shifts from voltage control to current control. If the
output voltage is pulled very low during a severe fault,
the current-limit circuit can exhibit either foldback or
tailout characteristics (output-current decrease or
increase). The unit operates normally once the output
current is brought back into its specied range.
Remote On/Off
To turn the power module on and off, the user must
supply a switch to control the voltage between the on/off
terminal and the VI(–) terminal (Von/off). The switch can be an open collector or equivalent (see Figure 11). A logic
low is Von/off = 0 V to 1.2 V, during which the module is on.
The maximum Ion/off during a logic low is 1 mA. The switch
should maintain a logic-low voltage while sinking 1 mA.
During a logic high, the maximum Von/off generated by
the power module is 15 V. The maximum allowable
leakage current of the switch at Von/off = 15 V is 50 A.
If not using the remote on/off feature, short the
ON/OFF pin to VI(–).
8-580 (C).d
Figure 11. Remote On/Off Implementation
Remote Sense
Remote sense minimizes the effects of distribution
losses by regulating the voltage at the remote-sense
connections. The voltage between the remote-sense
pins and the output terminals must not exceed the out-
put voltage sense range given in the Feature Specica-
tions table, i.e.:
[VO(+) – VO(–)] – [SENSE(+) – SENSE(–)]
≤ 0.5 V
The voltage between the VO(+) and VO(–) terminals
must not exceed the minimum value indicated in the
output overvoltage shutdown section of the Feature
voltage due to remote-sense compensation and output
voltage set-point adjustment (trim), see Figure 12.
If not using the remote-sense feature to regulate the out-
put at the point of load, connect SENSE(+) to VO(+) and
SENSE(–) to VO(–) at the module.
Although the output voltage can be increased by both
the remote sense and by the trim, the maximum
increase for the output voltage is not the sum of both.
The maximum increase is the larger of either the
remote sense or the trim. Consult the factory if you
need to increase the output voltage more than the
above limitation.
The amount of power delivered by the module is
dened as the voltage at the output terminals multiplied
by the output current. When using remote sense and
trim, the output voltage of the module can be
increased, which at the same output current would
increase the power output of the module. Care should
be taken to ensure that the maximum output power of
the module remains at or below the maximum rated
power.
8-651 (C).e
Figure 12. Effective Circuit Conguration for Single-
Module Remote-Sense Operation
Output Voltage Set-Point Adjustment (Trim)
Output voltage trim allows the user to increase or
decrease the output voltage set point of a module. This
is accomplished by connecting an external resistor
between the TRIM pin and either the SENSE(+) or
SENSE(–) pins. The trim resistor should be positioned
close to the module.
If not using the trim feature, leave the TRIM pin open.
With an external resistor between the TRIM and
SENSE(–) pins (Radj-down), the output voltage set point (VO, adj) decreases (see Figure 13). The following equa-
tion determines the required external-resistor value to
obtain a percentage output voltage change of
%.
+
Ion/off
–
Von/off
CASE
ON/OFF
VI(+)
VI(–)
SENSE(+)
SENSE(–)
VO(+)
VO(–)
VO(+)
SENSE(+)
SENSE(–)
VO(–)
VI(+)
VI(–)
IO
LOAD
CONTACT AND
DISTRIBUTION LOSSES
SUPPLY
II
CONTACT
RESISTANCE