Data Sheet
September 6, 2008
FNW700R Power Modules; DC-DC Converters
36 – 75 Vdc Input; 28Vdc Output; 700W Output
Feature Description (continued)
With an external resistor between the TRIM and
SENSE(-) pins (R
adj-down
), the output voltage set point
(V
o,adj
) decreases (see Figure 11). The following
equation determines the required external-resistor
value to obtain a percentage output voltage change of
Δ%.
For output voltages: 28V
⎛
100
⎞
R
adj
−
down
=
5.97
× ⎜
−
1
⎟
K
Ω
⎝ Δ
%
⎠
Where,
Δ
%
=
V
o, nom
−
V
desired
×
100
V
o, nom
V
desired
= Desired output voltage set point (V).
Figure 11. Circuit Configuration to Decrease Output
Voltage.
Trim Up – Increase Output Voltage
With an external resistor connected between the Vo(+)
and SENSE(+) pins
(
R
adj-up
),
the output voltage set point
(
V
o,
ad
j
) increases (see Figure 12).
The following equation determines the required
external-resistor value to obtain a percentage output
voltage change of
Δ%.
For output voltages: 28V
Figure 12. Circuit Configuration to Increase Output
Voltage.
The voltage between the V
o
(+) and V
o
(-) terminals must
not exceed the minimum output overvoltage shut-down
value indicated in the Feature Specifications table. This
limit includes any increase in voltage due to remote-
sense compensation and output voltage set-point
adjustment (trim). See Figure 13.
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.
The amount of power delivered by the module is
defined 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 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.
Examples:
To trim down the output of a nominal 28V module to
16.8V
Δ
%
=
28
V
−
16.8
V
×
100
28
V
∆%
= 40
R
adj
−
up
=
Where,
Vo, nom
× Δ
%
K
Ω
100
⎛
100
⎞
R
adj
−
down
=
5.97
× ⎜
−
1
⎟
K
Ω
⎝
40
⎠
R
adj-down
= 8.96 kΩ
To trim up the output of a nominal 28V module to 30.8V
Δ
%
=
V
desired
−
V
o, nom
×
100
V
o, nom
Δ
%
=
30.8V
−
28V
×
100
28V
V
desired
= Desired output voltage set point (V).
Δ%
= 10
R
adj
−
up
=
28
×
10
K
Ω
100
R
adj-up
= 2.8 KΩ
LINEAGE
POWER
8
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
