Delta Electronics Q48SP - Manual (Page 9)

DS_Q48SP12017_05302008
9
FEATURES DESCRIPTIONS (CON.)
Output Voltage Adjustment (TRIM)
(Not applicable to Q48SP120017Exxx)
To increase or decrease the output voltage set point,
connect 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-up (increase output
voltage)
If the external resistor is connected between the TRIM
and SENSE (+) pins, the output voltage set point
increases (Fig. 17). The external resistor value
required to obtain a percentage of output voltage
change △% is defined as:
) )( 22 . 10
511
225 . 1
) 100 ( 11 . 5 (
( _
Ω −
Δ
−
Δ
Δ + ×
=
K
Vo
up Rtrim
100 ) (
×
−
= Δ
Vnom
Vadj Vnom
Vo=Nominal voltage
Ex. When trim up to 13.2V from 12V
⇒
( )
Ω =
− −
Ч
+ Ч
= −
K
up Rtrim
3 . 489
22 . 10
10
511
10 225 . 1
10 100 12 11 . 5
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
1 2 3 4 5 6 7 8 9 10
Trim-Up percentage
Trim resistor value (K) )
Figure 18: Trim UP resistor selection
Figure 19: Circuit configuration for trim-down (decrease
output voltage)
If the external resistor is connected between the TRIM
and SENSE (-) the output voltage set point decreases
(Fig. 19). The external resistor value required to obtain
a percentage output voltage change △% is defined
as:
( )
Ω −
Δ
= Δ
k ) 22 . 10
511
( Rtrim_down
Ex. When trim down to 9.6V from 12V
Ω = Ω − = −
K K down Rtrim 33 . 15 22 . 10
20
511
0
50
100
150
200
250
300
350
400
450
500
550
1 10 100
Trim-Down percentage
Trim-resistor value (K) )
Figure 20: Trim DOWN resistor selection
The output voltage can be increased by both the remote
sense and the trim, however the maximum allowed
increase is the larger of either the remote sense spec or
the trim spec, 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.