Delta Electronics Delphi Q48DC 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 Vo(+) or
Vo(-). The TRIM pin should be left open if this feature
is not used.
Vo(+)
Trim
Rtn
Vo(-)
Figure 17: Circuit configuration for trim-down (decrease
output voltage)
If the external resistor is connected between the TRIM
and Vo(+) pins, the output voltage set point decreases
(Fig.17). The external resistor value required to obtain
a percentage of output voltage change △% is defined
as:
⎡
749
− = −
Rtrim down . 9
⎢
Δ
⎣
Ex. When Trim-down -25%(12.1V×0.75=9.08V)
⎡
749
− = −
Rtrim down . 9
⎢
⎣
25
Vo(+)
Trim
Rtn
Vo(-)
Figure 18: Circuit configuration for trim-up (increase output
voltage)
DS_Q48DC12003_03112008
R
trim-down
⎤
( )
Ω
46 K
⎥
⎦
⎤
( ) ( )
Ω = Ω
46 K 20 5 . K
⎥
⎦
R
trim-up
If the external resistor is connected between the TRIM and
Rtn the output voltage set point increases (Fig.18). The
external resistor value required to obtain a percentage
output voltage change △% is defined as:
197 ( )
− = Ω
Rtrim up K
Δ
Ex. When Trim-up +5%(12 .1V×1.05=12.71V)
197 ( )
− = = Ω
Rtrim up 39 4 . K
5
When using 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.
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