Features Descriptions CON | Delta Electronics Series H48SA guide

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 20: 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. 20). The external resistor value required to obtain a percentage of output voltage change △% is defined as:

	⎡⎛		12	⎞			⎤
	⎢	⎜		− 2⎟	⋅(100	+ Δ) + 100⎥
	⎢	⎜		− 2⎟	⋅(100	+ Δ) + 100⎥
Rtrim_up	⎢	⎝ 1.225		⎠			⎥kΩ
Rtrim_up	⎢						⎥kΩ
	⎣				Δ		⎦

Ex. When trim up to 13.2V from 12V

Δ= 100*(13.2-12)/12 = 10

	⎡⎛		12	⎞		⎤
	⎢	⎜		− 2⎟	⋅(100 + 10) + 100⎥

Rtrim_up	⎢	⎝ 1.225		⎠		⎥kΩ
					10
	⎣					⎦

Rtrim_up = 95.755 kΩ

DS_H48SA12025_05052008

Figure 21: 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. 21). The external resistor value required to obtain a percentage of output voltage change △% is defined as:

	⎛ 100		⎞
Rtrim_down	⎜		− 2⎟kΩ


	⎝	Δ	⎠

Ex. When trim down to 9.6V from 12V

Δ= 100*(12-9.6)/12 = 20

Rtrim_down = (100 − 2) kΩ

Rtrim_down = 3 kΩ

The typical resistor value can be seen in below figure22.

Output voltage	Ω	)
	Resistor value ( k	)
13.2V	95.8
12.6V	183.7
10.8V	8.0
9.6V	3.0

Figure 22: Trim resistor value example for popular output voltages

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.