DS_V48SC05017_06262013

E-mail: DCDC@delta.com.tw

http://www.deltaww.com/dcdc

P9

Output Voltage Adjustment (TRIM)

To increase or decrease the output voltage set point,

connect an external resistor between the TRIM pin and

the SENSE(+) or SENSE(-). The TRIM pin should be

left open if this feature is not used.

For trim down, the external resistor value required to

obtain a percentage of output voltage change △% is

defined as:

 



















K

down

Rtrim

22

.

10

511

Ex. When Trim-down -20% (5.0V×0.8=4.0V)





























K

K

down

Rtrim

33

.

15

22

.

10

20

511

For trim up, the external resistor value required to

obtain a percentage output voltage change △% is

defined as:























K

up

Rtrim

22

.

10

511

1.225

)

(100

Vo

11

.

5

Ex. When Trim-up +10% (5.0V×1.1=5.5V)

 





















K

up

Rtrim

1

.

168

22

.

10

10

511

10

225

.

1

)

10

100

(

0

.

5

11

.

5

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.

THERMAL CONSIDERATIONS

Thermal management is an important part of the

system design. To ensure proper, reliable operation,

sufficient cooling of the power module is needed over

the

entire

temperature

range

of

the

module.

Convection cooling is usually the dominant mode of

heat transfer.

Hence, the choice of equipment to characterize the

thermal performance of the power module is a wind

tunnel.

Thermal Testing Setup

Delta’s DC/DC power modules are characterized in

heated vertical wind tunnels that simulate the thermal

environments

encountered

in

most

electronics

equipment. This type of equipment commonly uses

vertically mounted circuit cards in cabinet racks in

which the power modules are mounted.

The

following

figure

shows

the

wind

tunnel

characterization setup. The power module is mounted

on a test PWB and is vertically positioned within the

wind tunnel. The space between the neighboring PWB

and the top of the power module is constantly kept at

6.35mm (0.25’’).

AIR FLOW

MODULE

PWB

AIR VELOCITY

AND AMBIENT

TEMPERATURE

SURED BELOW

THE MODULE

FANCING PWB

Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)

Figure 17: Wind tunnel test setup

Thermal Derating

Heat can be removed by increasing airflow over the

module. To enhance system reliability, the power

module

should

always

be

operated

below

the

maximum operating temperature. If the temperature

exceeds the maximum module temperature, reliability

of the unit may be affected.