E48SH datasheet(9/15 Pages) FTDI

9 / 15 page

E48SH3R330_05142009

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 18:

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:

()

−

down

Rtrim

511

Ex. When Trim-down -10%(3.3V×0.9=2.97V)

()

−

down

Rtrim

511

Figure 19:

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:

()

−

Rtrim

511

1.225

)

(100

Ex. When Trim-up +10%(3V×1.1=3.3V)

()

5.11 3.3

(100 10 )

511

10.2

90.1

1.225 10

Rtrim

×+

−

=−

−

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.

Frequency Synchronization

This product family can be synchronized with external clock

signal to the TRIM pin. This reduces system noise and

interference in multiple converter systems.

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