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APPLICATION INFORMATION

ADJUSTING THE OUTPUT VOLTAGE

SET

O

0.7

R

30.1 (k

)

6.49 (k

)

V

0.7

æ

ö

=

W ´

-

W

ç

÷

-

è

ø

(1)

+Sense

V

O

-Sense

GND

V

O

Adj

PTH08T250W

10

17

11

16

13

4

18

12

9

8

V

O

GND GND GND

AGND

R

SET

1%

0.05 W

C

O

+

+Sense

V

O

-Sense

GND

UDG-07049

PTH08T250W

SLTS278B – JUNE 2007 – REVISED AUGUST 2007

external resistor for a number of standard voltages, along with the actual output voltage that this resistance value

provides.

For other output voltages, the value of the required resistor can either be calculated using the following formula,

or simply selected from the range of values given in Table 3. Figure 11 shows the placement of the required

resistor.

3.3

1.62

3.298

2.5

5.23

2.498

2.0

9.76

1.997

1.8

12.7

1.798

1.5

19.6

1.508

1.2

35.7

1.199

63.4

1.001

Open

0.700

(1)

maximum allowable input voltage is a function of switching frequency, and may increase or decrease

when the SmartSync feature is utilized. Please review the SmartSync section of the Application

Information for further guidance.

(1)

resistor directly between pins 18 and 4, as close to the regulator as possible, using dedicated PCB traces.

(2)

affects the stability of the regulator.

Copyright © 2007, Texas Instruments Incorporated

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