Delta Electronics Delphi F48SA Datasheet page 10

FEATURES DESCRIPTIONS (CON.)
Output Voltage Adjustment (TRIM)
To increase or decrease the output voltage set point,
the modules may be connected with an external
resistor between the TRIM pin and either the
SENSE(+) or SENSE(-). The TRIM pin should be left
open if this feature is not used.
Figure 17: Circuit configuration for trim-down (decrease
output voltage)
If the external resistor is connected between the TRIM
and SENSE (-) pins, the output voltage set point
decreases (Fig. 18). The external resistor value
required to obtain a percentage of output voltage
change △% is defined as:
⎛ ⎞
1
:= ⎜ − ⎟ ⋅
Rt_dn 2 kΩ
⎝ ⎠
Δ
Ex. When Trim-down -10% ( 28V * (1 – 10%) = 25.2V )
1
Rt_dn = --------- － 2 = 8k
10%
DS_F48SA28025_12072007
Figure 18: Circuit configuration for trim-up (increase output
voltage)
If the external resistor is connected between the TRIM
and SENSE (+) the output voltage set point increases
(Fig. 19). The external resistor value required to obtain
a percentage output voltage change △% is defined
as:
( )
⎡
⋅ + Δ
Vo 1 1
⎢
:= − −
Rt_up
⎣
1.24 Δ ⋅ Δ
Ex. When Trim-up +10% (28.0V * (1+10%) = 30.8V)
28*(1+10%)
Rt_up = ------------------- － -------- － 2 = 236.39k
1.24*10%
The output voltage can be increased by both the remote
sense and the trim, however the maximum increase is
the larger of either the remote sense or the trim, not the
sum of both.
When using remote sense and trim, the output voltage
of the module is usually increased, which increases the
power output of the module with the same output
current.
Care should be taken to ensure that the maximum
output power of the module remains at or below the
maximum rated power.
⎤
⎥
⋅
2 kΩ
⎦
1
10%
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